Rinderknech, who sits 65th in the world rankings, had not recorded a Tour-level victory before 2021 but has now triumphed 15 times after cruising past Delbonis 6-4 6-4.
The Frenchman will meet eighth seed Dusan Lajovic in the second round in Antwerp, after the Serbian downed Richard Gasquet 7-6 (7-3) 6-1 on Monday.
The other first-round clash in Belgium saw Alexei Popyrin capitulate in the third set as he succumbed to a 4-6 6-3 0-6 defeat against world number 62 Botic van de Zandschulp.
Americans Jenson Brooksby and Brandon Nakashima also booked their places in the main draw. Brooksby defeated Norbert Gombos 6-4 6-2, while Nakashima overcame Pierre-Hugues Herbert 6-2 6-4.
Meanwhile in Russia, Cilic – who has claimed the crown in Moscow twice previously – recovered from a first-set scare in his round-of-32 tie with qualifier Damir Dzumhur, eventually triumphing 6-7 (4-7) 6-1 6-1.
John Millman experienced similar difficulties, with Benjamin Bonzi claiming the first set before the Australian succeeded 6-7 (5-7) 6-4 6-3 to set up a potential second-round match against fifth seed Alexander Bublik.
The former world number one, competing at the Moscow event for the first time since 2013, won 6-1 6-4 to set up a meeting with Veronika Kudermetova, who survived a marathon contest with qualifier Oksana Selekhmeteva.
Anett Kontaveit, who won the title in Ostrava last month, prevailed 6-3 6-3 against Katerina Siniakova. Another seed, Wimbledon quarter-finalist Ons Jabeur, retired against Ekaterina Alexandrova when trailing 6-1 1-0.
Andrea Petkovic also progressed when Jelena Ostapenko had to halt proceedings in their third set, while seventh seed Elena Rybakina lost in straight sets to Olympic silver medallist Marketa Vondrousova.
At the Tenerife Open, Camila Giorgi progressed past Aliona Bolsova 7-6 (7-4) 3-6 6-4 despite giving up two penalty games due to repeated indiscretions when line calls were called into question.
Fifth seed Viktorija Golubic lost in straight sets to Arantxa Rus, while Alison Riske was dispatched 6-1 6-4 by Donna Vekic.
Seventh seed Clara Tauson defeated Heather Watson via a final-set tie-break, while Varvara Gracheva won in the same vein against third seed Sara Sorribes Tormo in a match lasting nearly three and a half hours.
Top seed Elina Svitolina was one set up against Maria Camila Osorio Serrano when their match was suspended for the night.
World number 28 Kasatkina, who has won four WTA Tour titles, fell on home soil to Kalinina as the Ukrainian triumphed 6-2 6-3 on Monday.
Ajla Tomljanovic cruised past Liudmilla Samsonova in similar fashion, claiming a 6-2 6-4 victory in Moscow to set up a last-16 clash with top seed Aryna Sabalenka, who is ranked second in the world.
Anna Kalinskaya joins Tomljanovic in the next round as she defeated Dayana Yastremska 7-6 (7-5) 6-4 on home soil and the Russian will now face French and US Open semi-finalist Maria Sakkari.
Lesia Tsurenko had no issues against China's Qinwen Zheng as she won 6-4 6-3, while American Bernarda Pera beat Aleksandra Krunic 7-6 (7-3) 6-3 to seal her second-round berth.
Meanwhile, number two seed Zidansek, who sits 33rd in the world rankings, crashed out in Tenerife as world number 108 Jaqueline Cristian succeeded 7-5 4-6 6-1.
Zhang Shuai was the sixth favourite in Spain but she lost to fellow Chinese star Wang Xinyu 6-2 6-1, with Anna Karolina Schmiedlova also defeating Kaja Juvan 4-6 6-1 6-4 and Irina-Camelia Begu overcoming Marta Kostyuk 6-4 6-4.
The former world number one emerged triumphant from a gruelling contest lasting three hours and 45 minutes, the longest three-set match of the 2021 ATP season.
Having warded off two match points in the decisive tie-break, Murray clinched a 7-6 (7-2) 6-7 (7-9) 7-6 (10-8) victory with a drop shot that landed just out of Tiafoe's reach.
"I think that's the first time in my career I've played a 7-6, 6-7, 7-6 [match]. I don't think I've ever played a match like that," said Murray, who next faces second seed Diego Schwartzman. "I think it's the longest three-set match I've played by quite a distance. I'm tired right now, obviously it was an unbelievable battle.
"Nowadays obviously my body is old now. I've played a lot of matches on the tour. I don't mind playing long matches, but that was taking it to another level.
"Brilliant match, amazing atmosphere, thanks to everyone who came and supported. It's just so nice to be back and playing in front of crowds again."
American prospect Jenson Brooksby left his compatriot Reilly Opelka flummoxed as the fifth seed was beaten 6-4 6-4.
Opelka was heard proclaiming Brooksby was the "best player I've played in my whole life" during the second set as he struggled to interpret the 20-year-old's service game. Brooksby will face Botic van de Zandschulp in the next round.
There was another upset when sixth seed Alex de Minaur lost 6-4 6-0 to Brandon Nakashima, who has twice reached ATP-level finals this year and will next face Henri Laaksonen, victorious over Benoit Paire.
Lorenzo Musetti needed two tie-breaks to defeat fellow Italian Gianluca Mager, while Alejandro Davidovich Fokina – quarter-finalist at the French Open this year – eased past Jordan Thompson 6-3 6-3.
At the Kremlin Cup, fifth seed Alexander Bublik suffered a surprise straight-sets defeat to Illya Marchenko, the world number 164 winning by a 6-4 6-3 scoreline.
Adrian Mannarino battled through against wildcard Roman Safiullin, but Laslo Djere lost in three sets to Gilles Simon.
Ricardas Berankis and Egor Gerasimov also progressed, while Guido Pella retired from his match with Pedro Martinez.
Handed a bye for the opening round, third seed Khachanov made home advantage count in his first match as the Russian defeated Australian world number 50 James Duckworth 3-6 6-3 6-1 to reach the quarter-finals on Wednesday.
Khachanov – Olympic Games silver medallist, who triumphed in Moscow three years ago – will face another Australian, John Millman after he defeated Illya Marchenko 6-1 5-7 6-4 at the ATP 250 tournament.
"It always feel great to be back in your hometown, in a tournament where everything started for me as a professional tennis player," world number 31 Khachanov said.
"[This is] where I won my first matches, I got my first points. Since then, it's always great to come back home to see a crowd, [get] home support. It's also little bit more nervous, of course. But I always enjoy playing at home."
Khachanov was joined in going through to the last eight by sixth seed Marin Cilic – a two-time Kremlin Cup champion who overcame Tommy Paul 7-5 6-3.
At the European Open in Antwerp, top seed Jannik Sinner downed fellow Italian youngster Lorenzo Musetti 7-5 6-2 in the duo's first meeting as professionals.
"We never practice together, so it was kind of a new match," Sinner said post-match.
"He's an incredible player. He's a very great talent, so I hope we will have a couple of more matches on the pro tour, and obviously I'm very happy about my level today."
Arthur Rinderknech upstaged eighth seed Dusan Lajovic 6-3 4-6 6-2 to set up a quarter-final tie with Sinner, who is in the hunt for a fourth title of the season and a place at next month's ATP Finals in Turin.
Another emerging talent, qualifier Jenson Brooksby, bettered US Open quarter-finalist Botic van de Zandschulp 6-2 6-0, with Alejandro Davidovich Fokina sending third seed Cristian Garin packing 4-6 6-3 6-3.
Ninth seed Kontaveit ousted Vondrousova in Moscow on Saturday with a commanding 6-3 6-4 victory.
The Estonian had lost both of her previous two meetings with Vondrousova, but needed only an hour and 14 minutes to reach her fifth final this year.
Kontaveit struck 26 winners, with her backhand a potent weapon, and broke five times – three of those coming in the first set after she failed to hold in the first game of the match.
The 25-year-old Tallinn native has lost only two of her past 22 matches, while her winning run indoors now stands at nine.
Standing in the way of Kontaveit and a fourth title in 2021 is home hope Alexandrova, who advanced to her first WTA 500 final when Maria Sakkari retired due to dizziness.
Alexandrova was leading 4-1 in the opening set when the fourth seed from Greece decided she was unable to continue.
There will be an unseeded champion at the Tenerife Open after Colombian Camila Osorio beat Camila Giorgi 6-4 7-5.
Ann Li will play in her second title-decider of the year courtesy of an emphatic 6-2 6-1 triumph over Alize Cornet.
The 20-year-old American, who took a set off Novak Djokovic and rattled the world number one at the US Open, is shaping up as potentially his country's biggest hope for the future in the men's game.
Californian Brooksby crushed Spain's world number 44 Alejandro Davidovich Fokina 7-5 6-0, and second seed Schwartzman awaits after the Argentinian took down another 20-year-old American, Brandon Nakashima, scoring a 6-4 6-2 quarter-final win.
Schwartzman is the man who ended Andy Murray's hopes at the tournament in Antwerp.
Brooksby, who had to win two qualifying matches to reach the main draw, said: "Tomorrow will be a great match. I'm really looking forward to it. I'll get some rest tonight and get ready to battle again tomorrow."
The other semi-final will see Italian top seed Jannik Sinner take on South African seventh seed Lloyd Harris following their respective straight-sets wins over Arthur Rinderknech and Marton Fucsovics.
There will be an all-Russian semi-final at the Kremlin Cup in Moscow, after Aslan Karatsev and Karen Khachanov won through to the final four.
Second seed Karatsev sank the hopes of Frenchman Gilles Simon, breaking serve five times on the way to a 6-4 6-3 win, while third-seeded Khachanov edged out Australian John Millman. A 7-5 7-6 (7-4) grind featured 19 aces by Khachanov, the 2018 Kremlin Cup champion, who saved four set points in the second set.
Marin Cilic thrashed Pedro Martinez 6-1 6-2 to set up a tussle with Ricardas Berankis, the Lithuanian ending Adrian Mannarino's run with a 6-2 7-6 (7-1) success. Frenchman Mannarino had stunned Russian top seed Andrey Rublev in the previous round.
Mannarino ultimately came out on top 5-7 7-6 (7-4) 6-3 but he had to do it the hard way, coming back from match point down to set up a meeting with Ricardas Berankis, who lost only tree games in a 6-2 6-1 win over Federico Coria.
Rublev was never cruising, however, as Mannarino only just fell short in the first set and then took the second to a tiebreak, which he eventually won to turn the tide.
The 33-year-old, who lost to Rublev in the final two years ago, took things up a notch in the decider and did not face a single break point as he got the job done despite the home support.
"The crowd was cheering for Andrey but that is normal," he said after reaching the quarter-finals. "I was happy to play with such a nice atmosphere.
"We have been playing for a long time without fans, so it is nice to enjoy a stadium with crowds now."
Second-seed Aslan Karatsev is now the favourite in Moscow, and the Russian had few issues in a 6-4 6-3 defeat of Egor Gerasimov.
Karatsev will face Gilles Simon next following his 6-3 6-2 win over Mackenzie McDonald, while Pedro Martinez won 6-3 6-4 over Filip Krajinovic to book his passage.
At the European Open in Antwerp, Andy Murray's hopes of winning a first ATP Tour title in two years were ended by number two seed Diego Schwartzman.
The Argentinian trailed 4-1 in the first set but fought back to win 6-4 7-6 (8-6) in his first ever match against the Scot, whose last tour triumph was in Antwerp.
In his on-court interview, Schwartzman said: "It was a pleasure to play against Andy. We had not played before and he is coming back and every week he is playing better and moving better.
"I have a lot of respect because when I grew up playing tennis, I was watching Roger [Federer], Rafa [Nadal], Andy and Novak [Djokovic] and right now playing against him is a pleasure for me."
Seventh seed Lloyd Harris is also into the quarter-finals after a straightforward 6-2 6-3 victory over Jan-Lennard Struff in just 72 minutes, Marton Fucsovics came through 6-7 (5-7) 6-3 6-1 against Roberto Bautista Agut and Brandon Nakashima edged past Henri Laaksonen 7-6 (7-5) 6-7 (5-7) 6-3 to earn the right to face Schwartzman.
Top seed Sabalenka – appearing in Moscow for the first time – had not played since being downed by Leylah Fernandez, having tested positive for coronavirus on the eve of the Indian Wells Open.
The Belarusian, who sits second in the world rankings, profited from a bye in the first round before battling past Tomljanovic 7-6 (7-2) 4-6 6-1 on Wednesday as she fired 10 aces but made 30 unforced errors.
Sabalenka will now meet Ekaterina Alexandrova after the Russian cruised past Anhelina Kalinina 6-4 6-1, while Anastasia Pavlyuchenkova comfortably defeated Bernarda Pera 6-2 7-5.
Number two seed Garbine Muguruza also reached her seventh quarter-final of the season as she defeated Tereza Martincova 6-4 4-6 6-3 in just under three hours in Moscow.
Meanwhile, Elina Svitolina was shocked in the Tenerife Open as she was dumped out by Maria Camila Osorio Serrano, who succeeded 5-7 6-3 6-2 to claim her first top-10 victory.
Svitolina was the favourite in Spain and comfortably took the first set on Tuesday. However, inadequate light stopped play and the 19-year-old Osorio responded emphatically the following day to secure a memorable triumph.
Ann Li coasted past Varvara Gracheva 6-4 6-2 after Anna Karolina Schmiedlova had dispatched Jaqueline Cristian 6-2 7-5 in the opening match of the day.
Xinyu Wang retired injured against Alize Cornet, who led 4-1 in the decisive set, while Donna Vekic and Irina-Camelia Begu's match was suspended for bad light with the Croatian leading by a set.
The third seed was on court for just 34 minutes on Thursday as last-16 opponent Anna Kalinskaya was forced to retire through injury at 6-2 1-0 down.
Sakkari has enjoyed a successful year on the WTA circuit, reaching grand slam semi-finals for the first time in her career at the French Open and US Open.
Through to the quarter-finals in the Russian capital, where she will play Simona Halep, the 26-year-old becomes the first Greek woman to qualify for the year-end WTA Finals in Mexico.
Eighth seed Halep beat Veronika Kudermetova 6-1 7-6 (7-4), while world number 35 Marketa Vondrousova also prevailed in straight sets against Ukrainian Lesia Tsurenko.
Elsewhere, Ostrava Open champion Anett Kontaveit is through to her eighth quarter-final of 2021 after defeating Andrea Petkovic 6-1 6-4.
Meanwhile, at the Tenerife Open, fourth seed Camila Giorgi enjoyed a commanding 6-1 6-2 victory over Montenegro's Danka Kovinic.
However, there was no joy for seventh seed Clara Tauson as the Danish teenager went down 7-6 (7-4) 2-6 6-4 against China's Saisai Zheng.
The Greek star is chasing what would be just her second career title at WTA level, but the limited silverware belies her growing reputation: Sakkari has shot up to a career-high seventh in the world rankings during her best season on tour.
Looking to finish with a flourish, both in Moscow and next month at the season-ending WTA Finals, Sakkari scored a 6-4 6-4 victory over former world number one Halep on Friday.
The victory sets up a last-four clash with Ekaterina Alexandrova, after the Russian impressed a home crowd by landing a 6-3 6-4 win against top seed Aryna Sabalenka.
Yet Sakkari was almost reeled in by Halep from the point of victory in the second set, being unable to finish off the match on her own serve after building a 5-1 lead. Halep twice broke back, before dropping her own serve.
"It was a very tough match today," Sakkari said in an on-court interview. "It was the first time I'd played Simona, but I knew what to expect: she makes a lot of balls, more than any other player. I had a tough moment in the second set when I was 5-1 up, but finally, I found a way. I got a little nervous, a little bit tired.
"The last couple of months have been tough, I've been travelling a lot so haven't recovered enough. I just tried harder in the last game and just went for it."
Alexandrova's shock win over Sabalenka gave her a sixth career victory over a top-10 player. Second seed Garbine Muguruza followed Sabalenka out of the tournament, walloped 6-1 6-1 by in-form Estonian Anett Kontaveit, who has won 19 of her last 21 matches on tour, including beating Sakkari in the Ostrava final last month.
Kontaveit's semi-final opponent at the WTA 500 event will be Marketa Vondrousova, who claimed a 6-4 6-2 win over Anastasia Pavlyuchenkova.
At the Tenerife Open, Italian Camila Giorgi is the only seeded survivor in the semi-finals. The Italian fourth seed saw off Arantxa Rus 6-1 6-1, with Frenchwoman Alize Cornet and American Ann Li also among Friday's winners at the WTA 250 tournament.
Sinner, the number one seed, moved into his fifth final of the season with a 6-2 6-2 defeat of Lloyd Harris in Antwerp.
The 20-year-old Italian, who is in the hunt for a maiden ATP Finals spot, dominated Harris from the baseline and saved all three break points he faced.
There were only 16 unforced errors from the racket of the composed Sinner, who will be bidding to win his fourth title of the season on Sunday.
Sinner said: "I am very happy to be in the final. I just love playing here and love playing indoors, so hopefully I can play a great match again tomorrow."
Schwartzman ended 20-year-old American Jenson Brooksby's impressive run with a 6-4 6-0 victory.
The Argentinian struck 15 winners and secured five breaks as he marched into the championship match.
Russian second seed Aslan Karatsev will come up against Marin Cilic in his first final on home soil after knocking compatriot Karen Khachanov out of the Kremlin Cup.
Karatsev beat Khachanov 7-6 (9-7) 6-1, while sixth seed Cilic – a two-time winner of the tournament in Moscow – got the better of Ricardas Berankis 6-3 6-4.
Raducanu made history last month by becoming the first qualifier to win a major title with her triumph at Flushing Meadows, where she did not drop a single set all tournament.
However, the 18-year-old was beaten in her first match since that breakthrough success with a straight-sets loss to world number 100 Aliaksandra Sasnovich at the Indian Wells Open last week.
And Raducanu has now taken the decision to pull out of the Kremlin Cup in Moscow, which takes place next week.
In a statement released on Thursday, the Briton did not give a reason for her withdrawal but suggested she could return for the Transylvania Open later this month.
"Unfortunately I've had to make a tournament schedule change and won't be able to play Moscow this year, but I hope to compete there and in front of the Russian fans next year," said Raducanu, who is also due to compete at the Linz Open before the season is out.
"I look forward to returning to the tour in the next couple of weeks."
Speaking after her defeat to Sasnovich, Raducanu said she will need time to come to terms with her maiden grand slam triumph.
"I'm kind of glad that what happened today happened so I can learn and take it as a lesson. So going forward, I'll just have more experienced banked," she said.
"I think it’s going to take me time to adjust really to what's going on. I mean, I'm still so new to everything. I'm 18 years old. I need to cut myself some slack."
