The Australian started slowly in the quarter-final of the WTA 500 tournament on Friday as Pliskova broke her serve twice in taking the first set, before Barty hit back with three breaks of her own to force a decider.
Barty was two points away from losing on five occasions as world number nine Pliskova served for the match at 5-4 in the final set.
But she broke the Czech's resolve eventually, sealing victory when Pliskova hit the ball long after a baseline rally.
The win was Barty's eighth consecutive victory over a top-10 opponent and she said in a media conference afterwards that facing top players in the world brings the best out of her.
"When you come up against top-10 opponents, you have to go to that level above to be able to compete. They force you to bring your best," Barty said.
"With a lot of the girls in the top 10, we've had plenty of matches that have gone either way, different experiences, so each time I love that challenge of testing myself against the best."
Barty will face Elina Svitolina in the semi-finals after she saved two match points to claim a 6-7 (4-7) 7-5 6-2 victory over Petra Kvitova.
In the other half of the draw, Simona Halep breezed through to the semi-finals with a 6-1 6-4 win over Ekaterina Alexandrova.
Halep clinically closed out the first set, and although Alexandrova showed more fight in the second, the world number three did not allow her a route back into the match.
Halep will face Aryna Sabalenka following the Belarusian's 7-5 4-6 6-1 win over Anett Kontaveit.
In the Istanbul Cup, top seed Elise Mertens secured her place in the semi-finals with a 6-4 6-4 win over Katerina Siniakova.
Mertens will face Veronika Kudermetova who fought back from a set down to clinch a 2-6 6-3 6-3 win over Ana Bogdan.
The other semi-final will see Sorana Cirstea play Marta Kostyuk. Cirstea progressed after Fiona Ferro, trailing 6-4, retired through injury while Kostyuk beat Ana Konjuh 7-5 4-6 6-3.
The world number 12 eased to a 6-4 6-2 victory over the 17-year-old qualifier, who saved five match points in her final service game before Bencic closed things out.
"My love affair with clay is... I'm trying to improve myself on it," Bencic said after her first-round triumph.
"I think I'm getting better and I'm taking falls sometimes. I'm trying my best on this surface."
Maria Sakkari was similarly comfortable in progressing to the next round, hitting 24 winners as she dispatched Andrea Petkovic 6-2 6-2 on her debut at the tournament.
At the Istanbul Cup, four of the five scheduled matches were completed before rain stopped play with Anastasia Pavlyuchenkova and Anastasia Potapova level at a set apiece.
Eighth seed Wang Qiang fought back from a set down to beat Anastasia Gasanova 4-6 6-1 6-2.
There were also wins for Ana Konjuh, Katerina Siniakova and Viktorija Golubic.
The 26-year-old Canadian scored a 3-6 6-4 7-5 win over world number 92 Danka Kovinic at the clay-court event to book a semi-final against Spain's Paula Badosa.
Bouchard looked to have the tennis world at her feet in 2014 when she reached two grand slam semi-finals as well as her run to the title match at the All England Club.
Her career has followed a largely downwards trajectory but there have been signs that Bouchard, now a lowly 272nd in the rankings, might be set to climb again.
The Montreal-born player's last final came at the Malaysian Open four and a half years ago, when she lost in three sets to Elina Svitolina.
She had to come through qualifying to earn a main-draw place this week but the effort is paying off.
Bouchard battled what were reported to be shoulder issues in the win over Kovinic on Friday, and said it was a gutsy attitude that saw her win a match that lasted three hours and two minutes.
"I won because of not giving up, fighting, being tired physically and mentally. So I'm really proud of that," Bouchard said, according to the WTA website.
"It shows me that even though I wasn't feeling great before the match, at the start of the match and in the first set, that I can turn things around. There's always hope.
"It gives me a sense of confidence that I can give myself a chance, even when things aren’t going well."
Badosa beat Slovenian third seed Polona Hercog 4-6 6-3 6-4, with Czech player Tereza Martincova and Romanian Patricia Maria Tig setting up a semi-final clash in the bottom half of the draw after both had emphatic last-eight wins.
Former Wimbledon finalist Bouchard endured a miserable 2019 and tumbled down the rankings but reached the Prague Open quarter-finals in her previous outing before qualifying for the main draw in Turkey.
Once there, the Canadian made light work of Tomova, breaking serve six times for a 6-2 6-4 success.
Bouchard was joined in the second round by seeds Caroline Garcia, Alison Van Uytvanck and Misaki Doi.
However, both Garcia and Doi were taken to three sets, the former remarkably dropping the second 6-0 to home hopeful Cagla Buyukakcay while the latter came from behind to beat Ellen Perez.
Margarita Gasparyan, Patricia Maria Tig, Tereza Martincova and Danka Kovinic all also won on Wednesday.
The Romanian made short work of lucky loser Kamilla Rakhimova in a 6-4 6-1 straight sets victory in Turkey to launch her defence of the title she won against Elise Mertens last year.
The Belgian – top seed once again in Istanbul – gets her campaign underway against Sweden's Rebecca Peterson on Wednesday.
Elsewhere, there were wins for seeds Veronika Kudermetova and Jil Teichmann, though Tereza Martincova is out after a surprise 6-4 7-5 loss to qualifier Anna Bondar.
World number 12 Raducanu meanwhile is also poised to get her latest tilt for silverware underway in Stuttgart in midweek, with the eighth seed facing qualifier Storm Sanders.
The title is up for grabs on the WTA Tour following Ash Barty's retirement, with her world number one successor Iga Swiatek a potential quarter-finalist for the Briton if she gets that far.
There will be no Coco Gauff in the mix however after the American made a first round exit in straight sets, losing to Daria Kasatkina 6-4 6-2.
Seventh seed Ons Jabeur, meanwhile, fought back to beat Marketa Vondrousova 4-6 6-2 6-3, while qualifier Eva Lys overcame Viktorija Golubic 5-7 7-5 7-5 to set up a second round clash with Swiatek.
US Open champion Raducanu overcame Tamara Korpatsch 6-0 2-6 6-1 to set up a meeting with world number one Swiatek.
It will be the pair's first meeting on the WTA Tour and Raducanu's maiden encounter with a top-10 opponent.
The Briton, who is playing her first Tour-level clay-court event, won 90 per cent of points on her first serve in the opening set but that slipped to 56 per cent as she opened the door to a comeback in the second.
However, Raducanu rediscovered her composure in the decider and got over the line after an hour and 39 minutes.
Fourth seed Sakkari retired while 6-4 3-1 down to home hope Laura Siegemund, who will take on Liudmila Samsonova after she bested Pliskova 6-4 6-4.
Paula Badosa came through a third-set tie-break to beat Elena Rybakina 6-2 4-6 7-6 (7-4) and Aryna Sabalenka put a spanner in the works of Bianca Andreescu's comeback by taking their match 6-1 3-6 6-2.
Ons Jabeur beat Daria Kasatkina and Anett Kontaveit eventually ousted Ekaterina Alexandrova in a tie-break finale after surrendering the first set.
At the Istanbul Cup, third seed Veronika Kudermetova was granted a walkover against Ana Bogdan.
Seeds Ajla Tomljanovic (6) and Sara Sorribes Tormo (7) got past Lesia Tsurenko and Varvara Gracheva respectively, while there were also wins for Yulia Putintseva and Anastasia Potapova.
The world number one was far too good for her opponent, as she claimed her 6-1 6-1 victory in slightly over an hour.
Swiatek, 20, last lost a match in February and has not dropped a set since Indian Wells in March, winning each of the last 26 – that is the best such run on the WTA Tour since Serena Williams won 28 successive sets between the 2012 US Open and 2013 Australian Open.
Having won each of the past three events she has entered, Swiatek is the hot favourite to make it four on the bounce in Stuttgart, where she could meet reigning US Open champion Emma Raducanu next in the last eight.
Raducanu, seeded eighth, began her campaign with an emphatic 6-1 6-2 win over Australia's Storm Sanders on Wednesday to set up a second-round clash with Tamara Korpatsch – the winner faces Swiatek.
Sixth seed Karolina Pliskova overcame compatriot Petra Kvitova 6-4 4-6 7-6 (7-5) to progress, while Anett Kontaveit – the fifth favourite – saw off Angelique Kerber 3-6 6-4 6-4.
It was a bad day for some of the higher seeds in the Istanbul Cup, as three of the top five were eliminated.
Favourite Elise Mertens retired from her tournament opener with Rebecca Peterson due to a leg injury, though the Belgian was already 7-5 4-1 down.
Anhelina Kalinina and Jil Teichmann – seeded fourth and fifth, respectively – suffered surprise defeats as well.
Defending champion and second seed Sorana Cirstea appeared in danger of following them out as well, but rallied to defeat Arantxa Rus 3-6 6-1 7-5.
Ajla Tomljanovic also progressed, the Australian enjoying an impressive start against her countrywoman Jaimee Fourlis, winning 6-1 6-3.
World number one Swiatek landed a 21st consecutive victory as she edged out US Open winner Raducanu 6-4 6-4 in an hour and 45 minutes on the German clay.
There was plenty to admire from both players, but in the end it was another straight-sets success for Swiatek, who dropped only two games in her previous round against German Eva Lys.
It makes the 20-year-old Pole the first woman to win 28 consecutive sets on tour since Serena Williams, who did so from the 2012 US Open to the 2013 Australian Open.
Swiatek broke early in the first set to take charge, and with 19-year-old Raducanu battling a back problem the rankings leader soon got ahead in the second too.
This was Raducanu's first-ever match against a player ranked inside the WTA top 10, a peculiar statistic given she is already a grand slam champion.
Swiatek, like her opponent, knows how it feels to win a grand slam as a teenage surprise package, having triumphed as a 19-year-old at the 2020 French Open when ranked only 54th in the world.
At 4-3 in the second set of this contest, Swiatek saved two break points with clinical forehand winners out of the reach of Raducanu, shouting out in satisfaction moments later as she held serve to move a game away.
Raducanu had two more break chances in Swiatek's next service game but again could not convert as her opponent sealed victory.
Swiatek said: "I'm pretty happy that today's match was longer. Not for now, but for the future it's going to give me a lot of experience.
"Right now I want to play really aggressively, and I think this game style is going to fit the surface, and it fit the hardcourts as well."
She will face unseeded Liudmila Samsonova next after the Russian, playing as a neutral, beat Laura Siegemund 7-5 6-3.
The other semi-final in Stuttgart will see second seed Paula Badosa take on third seed Aryna Sabalenka.
Badosa was a 7-6 (11-9) 1-6 6-3 winner against Ons Jabeur, while Sabalenka fended off Anett Kontaveit 6-4 3-6 6-1.
At the Istanbul Cup, Friday saw quarter-final wins for Veronika Kudermetova and Anastasia Potapova, along with Sorana Cirstea and Yulia Putintseva.
Those results set up a semi-final on Saturday between second seed Cirstea and third seed Kudermetova, with Putintseva and Potapova also facing off.
The world number one produced a 22nd consecutive victory as she scraped a 6-7 (4-7) 6-4 7-5 win in a contest that lasted more than three hours.
The Pole will face third seed Aryna Sabalenka in Sunday's final on the German clay.
Swiatek broke early to race out to a 3-0 lead, but was pegged back by her Russian opponent, who fought hard to claim the first set on a tie-break.
The 20-year-old was looking to break the record of Serena Williams, equalling a feat of winning 28 sets in a row, but Samsonova prevented her from doing so.
It was the first time Swiatek had dropped a set since her Indian Wells Open last 16 match against Angelique Kerber in March, but she soon got back into her rhythm and clinched the second set 6-4.
She broke early again in the decider, but was once more broken back by a determined Samsonova, and Swiatek showed frustration with herself as she struggled to put away her opponent.
However, an unusually sloppy service game from Samsonova gave Swiatek another break in the 11th game of the set, which she closed out to seal her place in the final.
The other semi-final in Stuttgart saw Sabalenka overcome second seed Paula Badosa 7-6 (7-5) 6-4.
There were 14 double faults (seven each) in the match, but it was Sabalenka's big serve that ultimately led her to victory, hitting nine aces and winning 76.9 per cent of points on her first serve.
The Belarusian also saved six of eight break points faced as she ultimately eased past her Spanish opponent.
At the Istanbul Cup, third seed Veronika Kudermetova will play Anastasia Potapova in the final after seeing off second seed Sorana Cirstea in straight sets, 6-3 6-3.
Potapova had earlier come from a set down to beat Yulia Putintseva 2-6 6-2 6-2 in the other semi-final.
Swiatek was made to work hard in Saturday's semi-final against Liudmila Samsonova as she dropped a rare set, but she was back to her imperious best against Sabalenka.
The 20-year-old prevailed 6-2 6-2 in 84 minutes to make it 23 victories in a row – only five other different players have enjoyed longer winning runs since 2000.
With her latest triumph in Germany, Swiatek has now won 30 WTA matches in 2022, compared to 36 in the whole of 2021.
She has won the Qatar Ladies Open, Indian Wells and Miami Open in straight succession, having also reached the semi-finals of the Australian Open in January.
Sabalenka, who eliminated Paula Badosa, Anett Kontaveit and Bianca Andreescu en route to the final, was the latest player to fall short in trying to stop the sublime Swiatek.
After saving a break point in the opening game, Swiatek held serve and broke her opponent in the next game before comfortably seeing out the first set.
The Pole never looked under serious threat in the second set as she took the last four games to down world number four Sabalenka, who lost to Ash Barty in this final last year.
At the Istanbul Cup, meanwhile, Anastasia Potapova beat Veronika Kudermetova 6-3 6-1 to clinch her maiden career title.
Qualifier Potapova recovered from a set down to beat Yulia Putintseva in Saturday's semi-final and was too strong for Kudermetova in what was her third career final.
Kudermetova broke Potapova early on and led 3-1 in the opening set, but the latter soon found her range and took advantage of some sloppy mistakes from her opponent.
After battling to victory in the first set, Potapova looked far more comfortable in the second as she produced a number of impressive shots en route to a breakthrough triumph.
