The number two seed got off to a rocky start, finding himself 5-2 down in the first set before dramatically turning the tide, winning five straight games.
Rublev's first serve percentage improved from 49 to 58 in the second set as he stepped up his game against his Serbian opponent.
"Filip is one of my good friends, and we always have tough battles," Rublev said after his win. "So, today I was going on court thinking that it was going to be a really tough match, and when he started the way he did, I didn't know what to do because he was playing so good.
"Somehow I calmed myself and said 'OK, restart at the bottom and raise my level', and I started to play much, much better. I was able to turn the match around and finish the match in a good way."
He will face Alejandro Davidovich Fokina in the second round after the Spaniard took just 52 minutes to beat Malek Jaziri 6-2 6-0, converting all five of his break points as he strolled to victory.
Seventh seed Alexander Zverev had to come from behind to beat Jiri Lehecka 4-6 6-3 6-4, while Tallon Griekspoor set up a second-round clash with top seed Novak Djokovic after the Dutchman beat Constant Lestienne 6-4 3-6 6-2.
The 22-year-old Russian lost to Nikoloz Basilashvili in last year's final and will look to go one better after battling past Casper Ruud in the semi-finals on Saturday.
Rublev, aiming for a third title of 2020 and fifth of his burgeoning career, outfought Ruud on the way to a 6-4 6-2 win at the clay-court event.
"The match was really tough. I think everyone saw how tough it was, how [many] long rallies we had, how many chances both of us had," said Rublev.
He added, quoted on the ATP website: "It could [have been] easily 6-4, 6-2 to Casper’s side, but I was a little bit lucky. In the most important moments and at the end, the match was for me. I am really happy with the way I played today."
Rublev fell in the second round in Rome last week, following a run to the US Open quarter-finals, and his form has been inconsistent this year, yet sporadically brilliant.
Titles came in Qatar and Adelaide at the start of the year, and now another beckons in Germany.
The fifth seed said: "[It is] my first ever time that two years in a row I reached a final at the same tournament. For the moment, it is the most special tournament for me. We will see how it goes [on Sunday]."
Tsitsipas, seeded second, halted Chilean Cristian Garin in a three-set thriller he described as "nerve-wracking".
The Greek second seed will chase a second title of 2020 on Sunday, before joining Rublev in heading to the French Open.
A 7-5 3-6 6-4 success against Garin sent the world number six through to a 12th career ATP final, battle-hardened for the clash with Rublev.
The French Open also begins on Sunday, but Tsitsipas and Rublev are not due to begin their challenges in Paris on the opening day of the grand slam.
World number 12 Rublev, a two-time winner on the ATP tour this year, is seeded fifth in Hamburg and made light work of Sandgren.
Russia's Rublev broke his American foe three times and did not offer up a single break point on his own serve as he won 6-3 6-3 in an hour and nine minutes.
Elsewhere it was a productive day for qualifiers in the round of 32, with Pablo Cuevas and Jiri Vesely respectively seeing off Taylor Fritz and Gilles Simon in straight sets.
Despite the woes of his compatriots Sandgren and Fritz, Tommy Paul prevailed in a topsy-turvy encounter with Kevin Anderson.
The former Wimbledon and US Open finalist inflicted a bagel upon Paul to level matters in the second set but the world number 59 regrouped to triumph 6-4 0-6 6-4 - the big serving Anderson's 14 aces to his opponent's one counting for little in the final analysis.
Rublev had won 23 consecutive matches at this level, second only to Roger Federer (28), but Karatsev finally ended the Russian's remarkable run to progress to his first ATP singles final.
Karatsev, who incredibly went from qualifying to the semi-finals of the Australian Open this year, defeated his compatriot 6-2 4-6 6-4.
He became the first Wild Card to reach the final since Thomas Muster in 1997, doing so by hitting 41 winners and forcing 16 break points – of which he won four – during two hours and 12 minutes on court.
"It was a really tight match [against a] tough opponent," Karatsev said in his on-court interview.
"It was an unbelievable performance [from Andrey]. He didn't lose a match at an ATP 500 in [one year]. Everything was decided in one or two points, I feel happy."
The championship match will be between two first-time Dubai finalists after Lloyd Harris stunned Denis Shapovalov in the other semi-final.
World number 81 Harris, who overcame top seed Dominic Thiem, 14th seed Filip Krajinovic and former US Open finalist Kei Nishikori to reach the last four, came from a set and 4-2 down to defeat world number 12 Shapovalov.
He prevailed 6-7 (5-7) 6-4 7-6 (8-6) to reach a maiden ATP 500 final and become the first qualifier to reach the showpiece in Dubai.
"I don't have many words right now. I am super happy with that win," Harris said on court afterwards.
"Being a set and 2-4 down is mentally and physically a little bit troublesome for me, but I found my best tennis from there. I am just extremely happy with the result right now."
A recent US Open quarter-finalist, world number 69 Van de Zandschlup claimed the first top-10 win of his career on Friday.
The 26-year-old also advanced to the semi-finals of an ATP event for the first time.
There, he will face 2011 champion Marin Cilic, who was a 6-4 3-6 6-3 winner over third seed Roberto Bautista Agut.
Denis Shapovalov was another big-name casualty in Russia, the second seed going down 4-6 3-6 against world number 53 Jan-Lennard Struff.
Although, there were better fortunes for fifth seed Taylor Fritz. The Indian Wells semi-finalist is yet to drop a set this week after prevailing 6-4 6-2 against John Millman.
Elsewhere, Matteo Berrettini was the victim of another upset at the Erste Bank Open in Vienna.
The Wimbledon champion went down 1-6 7-6 (7-2) 6-7 (5-7) following a two-hour 40-minute battle with Carlos Alcaraz.
Reaching his first ATP 500 semi-final, the Spanish teenager claimed another big scalp having defeated Stefanos Tsitsipas at Flushing Meadows last month.
However, second seed Alexander Zverev remained on course for a fifth title of the season, as he claimed his 300th tour-level win.
The Australian Open finalist beat Felix Auger-Aliassime 6-4 3-6 6-3, avenging his fourth-round defeat by the Canadian at Wimbledon in July.
As the French Open began, Rublev and Tsitsipas were almost 600 miles away in northern Germany, duking it out for ATP Tour silverware.
Both will arrive in the French capital after a string of fine clay-court results; however, Rublev will be the happier man after a 6-4 3-6 7-5 success in the final saw him pocket the €79,330 winner's cheque.
Rublev pouched trophies at the start of the year in Qatar and Adelaide, and only Novak Djokovic has won more matches on the tour this season than the 22-year-old Russian's haul of 25 victories.
After they split the opening two sets, It seemed a sure thing that Greek world number six Tsitsipas would wrap up the title after surging to a 5-3 lead in the decider.
However, he could not get across the line, with Rublev landing his first title at ATP 500 level by reeling off four successive games.
Tsitsipas was seeking his second title of 2020, having won in Marseille in February, but his win-loss record in ATP finals now stands at 5-7, with his inability to close out this match posing questions about his prospects of competing deep into the coming fortnight in Paris.
Rublev has only played the French Open once, losing in the first round three years ago. He faces an opener against American Sam Querrey, while Tsitsipas starts against Spain's Jaume Munar.
Rublev was leading 6-4 6-1 when Anderson pulled out with a leg injury, which he had earlier led to a medical timeout for treatment.
The Russian, who has won 18 of his past 19 matches, will take on Lorenzo Sonego in Sunday's final, the Italian following up his stunning quarter-final victory over Novak Djokovic with a 6-3 6-4 win over Dan Evans.
Rublev is on the brink of qualifying for the season-ending ATP Finals in London next month, but the 23-year-old insists he is not setting any expectations and simply wants to continue with the relaxed approach that has served him so well in 2020.
"I don't know why it's going so well," he said. "I have such an amazing team and such amazing friends around me that always support me. That's probably why I'm playing so well.
"I came here thinking that I have nothing to lose. I have already played a really great season, so I came here to enjoy it, do my best, fight for every point and now here I am in the final.
"I want to keep thinking the same way and we'll see what's going to happen tomorrow."
Sonego, meanwhile, admits he can scarcely believe he made the final after initially losing in the final round of qualifying against Aljaz Bedene, only to get into the main draw once Diego Schwartzman.
He becomes the first lucky loser to reach the Vienna Open final since Andreas Haider-Maurer in 2010.
"It's amazing," Sonego said. "I started this tournament [by losing] in the qualifiers. It's not easy after losing my [qualifying] match to win four matches and now I got to the final.
"I don't have any expectations. I go with confidence and I [will] try to do my best tomorrow."
Chardy managed to save match points in the second set, as Rublev wobbled at the crucial moment, but the Russian got the job done 7-6 (7-2) 6-7 (2-7) 6-4.
The pair were on court for just under two hours and 40 minutes and racked up a considerable number of winners, with Rublev's 44 eight more than the Frenchman.
His 18-match winning streak in ATP 500 events has only been bettered on five previous occasions since 2009, all of which were achieved by Andy Murray, Rafael Nadal or Roger Federer, who holds the record of 28 successive victories.
If he is to get any closer to Federer's remarkable haul, Rublev will have to go beyond Tsitsipas, but Friday's match took plenty out of him.
"I will try to do as much as I can to be ready for [the semi-final]… Stefanos also had two tough matches [this week]," said Rublev.
"He had three sets [on Thursday] and today he had three sets. Now he has to play doubles. It is not easy."
As Rublev alluded to, Tsitsipas certainly did not have it all his own way against another Russian, Karen Khachanov, coming from a set down to win 4-6 6-3 7-5.
Tsitsipas also had to contend with being 3-1 down in the third set – but Rublev knows all about the Greek's ability to come back from the brink having lost to him in last year's ATP Finals despite having match point.
"He [Khachanov] was playing great tennis and I wasn't sure if I would be able to compete," Tsitsipas said after the contest.
"I had an amazing 5-0 lead in the second set and that brought a lot of confidence into my game. We had great rallies and the quality of tennis was excellent. You need to stay as calm as possible in three-setters. I have won a lot in the past and with experience, it gives me an idea of how to play in these tight moments."
Borna Coric and Marton Fucsovics will go head-to-head in the other semi-final.
Croatian Coric came through in straight sets against Kei Nishikori, though it was by no means a straightforward victory as he was pushed to tie-breaks in both sets, winning 7-6 (7-2) 7-6 (7-4).
Fucsovics saw off Tommy Paul 6-4 6-3 to reach the last four.
Fifth-seed Rublev, victorious in Hamburg and St Petersburg in recent weeks, was the highest-ranked player in action on Monday and never looked in any danger of being on the wrong end of an upset, coming through 6-3 6-2.
He broke Gombos in the second game of the match and did not have to save any break points in return across the entire contest.
Gombos dropped his serve again early in the second and that effectively doomed him, as Rublev – who is closing in one of the last two spots at the ATP Finals – cruised to victory. Casper Ruud or Jannik Sinner await in the last 16.
Gael Monfils' hopes of reaching the season-ending tournament took a hit, however, as injury forced him to bow out while 6-1 2-0 down to Pablo Carreno-Busta, who is also in with an outside chance of qualifying.
Eighth-seed Denis Shapovalov crashed out 6-4 7-5 to wildcard Jurij Rodionov, while Borna Coric beat Taylor Fritz 6-4 6-4. He will face either world number one Novak Djokovic or Filip Krajinovic.
Among the other big names competing in Austria are Stefanos Tsitsipas, Daniil Medvedev and Dominic Thiem.
The 22-year-old Norwegian has rocketed from outside the top 50 to 16th currently in the world rankings in just 18 months, and he is the top seed this week in Sweden.
Such a status is all rather novel for Ruud, but he breezed to a 6-0 6-2 win over 18-year-old Danish wildcard Holger Vitus Nodskov Rune on Thursday.
That carried him through to a quarter-final meeting with Swiss player Henri Laaksonen.
Ruud is back on clay this week, having enjoyed great success on the surface already this season, reaching semi-finals of the Masters 1000 events in Madrid and Monte Carlo, while also winning a title in Geneva.
A first-round exit on the Wimbledon grass followed those positive results, so another event on clay comes as a boost.
"It is a surface I have had the most success of my career, it is great to be back here in Bastad," Ruud said after crushing Rune's hopes.
"There is a bit of extra pressure [being the top seed]. In a match like this against a fellow Scandinavian younger player, it is even more."
He added, quoted by the ATP website: "I think I was very professional in my mindset today. I played a match without any errors really from the first to the last point.
"It is a nice feeling being the top seed but also pressure. I felt great crowd support, it is nice to feel that energy."
Qualifier Laaksonen beat Elias Ymer 6-2 7-5, while third seed Fabio Fognini was bounced out of the tournament, losing 6-3 1-6 6-4 to Spain's world number 97 Roberto Carballes Baena, who will tackle Slovakian Gombos in the last-eight stage on Friday.
At the Hamburg European Open, Pablo Carreno Busta justified his standing as second seed with a 7-5 6-3 win over fellow Spaniard Carlos Taberner to reach the quarter-finals.
Stefanos Tsitsipas is the top seed this week at the tournament in Germany and won through to the last eight on Wednesday.
Others to move through the rounds in Hamburg on Thursday included Dusan Lajovic and Federico Delbonis, the latter advancing with a handy 6-3 7-6 (7-4) win over fourth seed Albert Ramos-Vinolas.
The French Open runner-up struggled to get going as he fell to a 7-6 (7-4) 7-6 (7-2) defeat to the world number 180, who was backed by a boisterous home crowd throughout.
Ruud struggled from the off as Peniston forced four break points in the Norwegian's first service game, and his miserable outing was rounded off when his opponent raced into a 5-1 lead before serving out a second-set tie-break.
After claiming the scalp of the world number five, Peniston told the BBC: "I can't really believe it. It feels like a dream. It doesn't feel real.
"I think I've been playing well. Casper is an unreal player and he did so well at the French Open, so I knew it was a tough ask. Four or five years ago I was sitting in the crowd just watching so to be here now is just unreal."
Ruud was not the only big name to fall at the first hurdle, with fifth seed Diego Schwartzman going down 6-1 6-4 against big-serving Sam Querrey to become the fourth of the top five seeds to fail to reach the round of 16.
Second seed and defending champion Matteo Berrettini is the exception after faring much better against another home favourite, cruising past Dan Evans 6-3 6-3, while Stan Wawrinka downed Francis Tiafoe 7-6 (7-2) 6-7 (6-8) 7-6 (7-5), and Denis Shapovalov's clash with Tommy Paul was suspended by darkness at one set apiece.
Elsewhere, world number six Stefanos Tsitsipas progressed through his opening match at the Halle Open, beating Benjamin Bonzi 7-6 (7-1) 1-6 6-3 to set up an enticing last-16 clash with Nick Kyrgios, who bested Daniel Altmaier 6-3 7-5.
Fourth seed Felix Auger-Aliassime also progressed after being taken to three sets, beating Marcos Giron 6-3 5-7 6-3.
Meanwhile, defending champion Ugo Humbert will face a tough round-of-16 match against fifth seed Hubert Hurkacz after the Pole overcame Maxime Cressy 6-4 4-6 6-4.
The third seed struck 26 winners en route to a 7-5 6-4 triumph on Thursday, but it was his serve that pleased him most.
Shapovalov, ranked 12th in the world, sent down 10 aces as Frenchman Chardy was deprived of any break-point openings.
"I've focused on my serve a lot in the past couple of weeks," the Canadian said.
"I have worked on placing it and tried out different types of serves to have more variation. I hope I can continue that.
"I've also worked on my footwork and positioning during rallies. I am feeling the ball well on both sides. If I am moving well, everything goes into place."
Harris was a surprise winner over Kei Nishikori, sealing a 6-1 3-6 6-3 success to dump out the former world number four.
Second seed Andrey Rublev defeated Marton Fucsovics 7-5 6-2 and will now face fellow Russian Aslan Karatsev.
Wildcard Karatsev continued his run with a hard-fought victory over teenager Jannik Sinner, coming from a set down in a 6-7 (5-7) 6-3 6-2 win.
Rublev beat Henri Laaksonen 6-4 6-4 on Tuesday, while top seed Tsitsipas went the distance before edging out Alejandro Davidovich Fokina 7-5 6-7 (1-7) 6-4 after two hours and 39 minutes on the court.
Reflecting on his win, Tsitsipas was full of praise for his opponent, saying: "It was a great battle; he gave me some of the best tennis I have seen him play.
"He was very fired up today and making the best out of every single shot. He was hitting huge winners from behind the baseline. He's one of the best young players who I have played."
However, world number 12 Shapovalov had no such luck, as he slumped to a surprise defeat to Czech qualifier Jiri Lehecka.
The world number 137 saw off the Canadian 6-4 6-4, showing impressive resolve to hold serve at 4-2 in the first set after initially going 0-40 down.
Shapovalov converted just one of 11 break points offered up by Lehecka as he failed to build on an impressive run to the Australian Open quarter-finals last month.
Aslan Karatsev, who won a title in Sydney in January, was another seed to drop out, after his 2-6 7-6 (7-2) 7-6 (7-0) defeat to home favourite Tallon Griekspoor.
Griekspoor has enjoyed some big wins in this tournament in the past, having defeated Stan Wawrinka and Karen Khachanov in 2018 and 2019 respectively.
Khachanov, too, was in action on Tuesday; unlike his Russian compatriot Karatsev, Khachanov took his place in round two with a 6-7 (4-7) 6-1 7-6 (7-6) defeat of Alexei Popyrin.
Lorenzo Musetti and Dutchman Botic van de Zandschulp also progressed.
Sinner won his fourth title of what has been an outstanding season for the Italian in Antwerp last weekend and is only 110 points adrift of Hubert Hurkacz in the battle for the final place in the season-ending event in Turin.
Murray did the 20-year-old a favour by knocking Hurkacz out of the ATP 500 tournament in the Austrian capital on Monday and seventh seed Sinner eased to a 6-4 6-2 win over American Opelka two days later.
Sinner, who will overtake Pole Hurkacz if he reaches the semi-finals this week, won 93 per cent of points behind his first serve and did not face a break point in a resounding win and will play Dennis Novak in the second round.
Murray beat Alcaraz at Indian Wells this month, but the 18-year-old rising star from Spain turned the tables on the three-time grand slam champion with a 6-3 6-4 second-round win in Vienna.
Former world number one Murray struggled with his serve and was broken five times as he made an early exit.
Third seed Matteo Berrettini beat Nikoloz Basilashvili 6-7 (5-7) 6-2 6-3 to reach the third round, while Diego Schwartzman, Gael Monfils and Lorenzo Sonego moved into the second round.
In the St Petersburg Open, defending champion Andrey Rublev beat Ilya Ivashka 6-4 6-4 to reach the quarter-finals along with Denis Shapovalov, a 2-6 6-3 6-0 winner against Pablo Andujar.
Jan-Lennard Struff also moved into the last eight, with Karen Khachanov and Marin Cilic securing first-round wins.
The 19-year-old rising star, who won the Great Ocean Road Open last month, prevailed in a match that remained in the balance until the end on Wednesday.
Sinner won 6-4 3-6 7-5 to reach the quarter-finals, with Bautista Agut following top seed Dominic Thiem - who lost in the second round - out of the tournament.
After hitting 16 aces, Sinner – the youngest player in the ATP Tour top 100 – will face surprise Australian Open semi-finalist Aslan Karatsev next.
Second seed Andrey Rublev is through after a comfortable 6-3 6-1 win over Taylor Fritz.
Rublev will face Marton Fucsovics, who ousted Serbian Dusan Lajovic in three sets, in the last eight.
The Russian now has 22 consecutive wins at ATP 500 events, a run that has included four titles at that level. Only Roger Federer has ever recorded a longer streak, doing so with a run of 28 between 2014 and 2016.
"I am really happy that I can win in straight sets and quite confidently," Rublev said.
"I know Taylor since [the] juniors and it is always tough to play against him, because he has a huge serve and he is playing really fast.
"The first set was not even rallies because everything was serve, winner or serve, mistake, so everything was so fast.
"In these conditions, it is tough to find the rhythm. You don't know what's going to happen and it's really not easy, but I'm happy that in the end I made it."
Third seed Denis Shapovalov is also through after a 6-4 6-3 win over Hubert Hurkacz, the Canadian booking a last-eight meeting with Jeremy Chardy.
Kei Nishikori will play Lloyd Harris in the other quarter-final.
Italian 19-year-old Sinner is a fast-rising new star of the men's game and now has a ranking to match his age. However, he was put in his place by Novak Djokovic last week in Monte Carlo, before the world number one was himself dealt a jolting defeat by Dan Evans.
Sinner sped past Belarusian Egor Gerasimov in the first round in Barcelona on Tuesday, winning 6-3 6-2, and it will be wily world number 11 Bautista Agut who stands in his way of going deeper into the tournament.
In two meetings on hard courts this season, Sinner has edged out 33-year-old Spaniard Bautista Agut in tight deciding sets, and now they face a reunion on clay.
"He lost in Dubai against me, he lost in Miami against me, now we play once more here, so it's quite a small period of time," said Sinner.
"We're playing now our third match already, so it's going to be a very tough match. He is very, very solid. I never played against him on clay. I'm trying to be ready in the best possible way."
Bautista Agut barged past fellow Spanish player Pablo Andujar, scoring a 6-4 6-0 win.
Sinner was proud to enter the ATP top 20 this week but sees it as just a step on his journey, saying: "Obviously it's a good number, but for me at the moment not that important."
He added, quoted on the ATP website: "[I'm] just trying to improve day after day with my team and trying to improve as a player and the ranking is what it is. I'm happy to be top 20 player but the road is long so a lot of work to do."
Albert Ramos-Vinolas, Lorenzo Musetti and Frances Tiafoe, who fought off 17-year-old Spanish prospect Carlos Alcaraz, were also among Tuesday's winners in Barcelona.
Star turn Djokovic begins his campaign at the Serbia Open on Wednesday when he tackles Kwon Soon-woo, with the 18-time grand slam winner having received a first-round bye.
Tuesday's play in Belgrade saw wins for, among others, Federico Delbonis, Aljaz Bedene and Miomir Kecmanovic.
After losing the first set, the world number 10 staved off defeat in a nerve-wracking second-set tie-break.
The fourth seed clung on as Davidovich Fokina saw a trio of opportunities to clinch a shock win go begging, the Spaniard made to pay as his Italian counterpart fought back to prevail 4-6 7-6 (8-6) 6-3.
Sinner, who will next face former world number one Andy Murray, said: "It was a very tough match. I know him, but we've never played against each other.
"It was the first time for both of us and it was a tricky one, saving three match points. On the first one I got lucky because it was out, but not so far [out]."
Second favourite Andrey Rublev won both the singles and doubles titles in Marseille last week and continued his fine form with a 6-4 7-5 win over Daniel Evans that saw the Russian send down 28 winners.
Sixth seed Denis Shapovalov had to recover from a set down to see off Marton Fucsovics, though fifth seed Hubert Hurkacz enjoyed a more routine straight-sets triumph over Alexander Bublik.
Eighth seed Roberto Bautista Agut made relatively light work of Arthur Rinderknech but defending champion and seventh seed Aslan Karatsev was stunned 7-5 6-3 by Mackenzie McDonald.
Karen Khachanov needed a little shy of three hours to beat Alex de Minaur, his dubious reward a second-round clash with Novak Djokovic as the world number one continues his return to the Tour following his controversial Australian Open absence.
Competing in his debut ATP Tour tournament, 18-year-old wildcard Nakashima defeated British qualifier Cameron Norrie 7-5 6-2 on Wednesday.
Nakashima, who is coached by 1987 Wimbledon champion and two-time Australian Open runner-up Pat Cash, is the event's youngest quarter-finalist since Kei Nishikori won the tournament as an 18-year-old in 2008.
"I always knew that I had the game to compete with these high-level pros. I just had to have the right opportunities," said Nakashima, who will face Yoshihito Nishioka after the Japanese blitzed Noah Rubin 6-1 6-2.
"I was just hoping to play a good first-round match here, but after winning these two matches, I have a lot of confidence in my game now… Hopefully I can keep it going."
Reilly Opelka – the fourth seed – dismantled Mackenzie McDonald 6-3 6-4 and Kwon Soon-woo prevailed 6-4 3-6 7-6 (7-0) against Ryan Harrison.
At the Rio Open, third seed Garin beat Federico Delbonis 6-4 6-3 en route to the quarters in Brazil.
Garin, who claimed the Cordoba Open title almost a fortnight ago, hit 22 winners to earn a meeting with Federico Coria after the Argentinian's 6-4 4-6 6-4 victory over Carlos Alcaraz.
Elsewhere, lucky loser Attila Balazs rallied past Thiago Monteiro 1-6 6-1 6-4 and Pedro Martinez trumped fellow Spaniard Pablo Andujar 6-1 6-4.
Three-time grand slam winner Murray has a 19-11 win-loss record in 2022 and wants to improve that substantially before the year is out.
In March, the Scot pledged to donate the rest of his season's winnings to UNICEF's Ukraine mission, as the country endures a heavy toll of death and destruction during Russia's invasion.
A disappointing second-round loss to John Isner at Wimbledon was followed by a quarter-final exit to Alexander Bublik at the Hall of Fame Open in Newport, with those results not meeting Murray's expectations.
He is being driven by his own hunger for better results, but also an eagerness to put together a big pot of money for UNICEF's appeal.
Citi Open chairman Mark Ein announced his foundation would match Murray's winnings this week and commit that sum to the effort in Ukraine.
"You can't just forget about this," Murray said of the war. "It's still going on. People are still getting killed, children are still having to flee their homes, and are in really, really tragic situations.
"I think it's important that the media continues to shine a light on it, keep talking about it. Hopefully what the tournament is doing here can help a little bit with that.
"I just want to try and win as many matches as possible and raise as much money as I can. It will be a significant amount hopefully by the end of the year. Hopefully it makes a difference."
Stiller is a big tennis fan and has often been seen in front-row seats at the sport's top events.
He tweeted: "So much respect for @andy_murray shining a light on the millions of people - and children - still affected by this senseless war in #Ukraine."
The Reality Bites, Zoolander and There's Something About Mary actor has been a long-time Murray fan, meeting him at the 2013 US Open, a year after the British star took the Flushing Meadows title.
Murray, 35, begins his challenge at the Citi Open, staged in Washington, DC, against Sweden's Mikael Ymer on Monday.
He hailed Ein's Ukraine pledge as "brilliant", adding: "I think it really helps. It shows when the players and the tournaments work together, that really good things can happen." week.”
Thiem, playing his first tournament since reaching the Australian Open final, was pushed by Jaume Munar before winning 6-7 (5-7) 6-3 6-4 on the clay in Brazil.
The Austrian top seed, who won the ATP 500 event in 2017, needed two hours, 41 minutes to advance, having also dropped a set in his opener.
Thiem will face Gianluca Mager in the quarter-finals after the Italian qualifier's 6-3 7-6 (7-5) victory over Joao Domingues.
Borna Coric moved into the last eight courtesy of a 6-3 1-6 7-6 (7-5) win against wildcard Thiago Seyboth Wild.
The fifth seed will meet Lorenzo Sonego, who upset second seed Dusan Lajovic 7-6 (7-5) 7-6 (7-5).
At the Delray Beach Open, Raonic – the 2017 runner-up – served 11 aces in a 7-5 6-3 win over Cedrik-Marcel Stebe that sent him into the quarter-finals.
Steve Johnson awaits the Canadian after overcoming 2017 champion Jack Sock 6-4 5-7 6-1.
Frances Tiafoe, the 2018 winner, and Ugo Humbert set up a last-eight meeting with straight-sets victories over Tommy Paul and Miomir Kecmanovic respectively.
