Former world number one Novak Djokovic and reigning Cincinnati Masters champion Grigor Dimitrov advanced, while Alexander Zverev was bundled out.
Wimbledon champion and 10th seed Djokovic overcame a slow start to reach the last 16 with a win over Adrian Mannarino on Wednesday.
Dimitrov opened his title defence by prevailing against Mischa Zverev, whose younger brother and third seed Alexander suffered a shock second-round defeat midweek.
There were also wins for seeds Kevin Anderson, Marin Cilic and David Goffin, while Stan Wawrinka was too good for Kei Nishikori.
The clash between Juan Martin del Potro and Hyeon Chung failed to get underway due to rain.
DJOKOVIC FINISHES FAST TO ADVANCE
The 13-time grand slam champion continued his quest for a maiden Cincinnati title with a 4-6 6-2 6-1 victory.
Djokovic – a five-time finalist at the ATP Masters 1000 event as he seeks to become the first man to complete the Career Golden Masters – was sloppy early but recovered by break five times en route to victory.
"I think it adds more to the motivation rather than pressure," the 30-time Masters champion said. "I really want to win this tournament, and I have been trying. I'm still in the tournament this year, and hopefully I can get a shot at the title."
It does not get any easier for Djokovic, with Dimitrov waiting in the next round.
Fifth seed Dimitrov – who has only won one of the past nine meetings against Djokovic – topped Mischa Zverev 7-6 (7-5) 7-5.
ZVEREV STUNNED BY HAASE
There was a major shock in Cincinnati, where Alexander Zverev went down 5-7 6-4 7-5 to Robin Haase.
A beaten quarter-finalist at the Rogers Cup last week, Zverev is still waiting for his first main-draw victory at the tournament following four defeats.
Haase will play Pablo Carreno Busta for a spot in the quarters after the 13th seed defeated Bradley Klahn 6-4 6-4.
CILIC MAKES WINNING RETURN
Australian Open runner-up and world number seven Cilic outlasted qualifier Marius Copil 6-7 (4-7) 6-4 6-4.
Cilic – who will take on Karen Khachanov – was playing his first Cincinnati match since winning the title in 2016.
South African sixth seed Anderson and 11th seed Goffin will go head-to-head in the round of 16.
Anderson trumped Jeremy Chardy 7-6 (8-6) 6-2, while Goffin rallied past Benoit Paire 5-7 6-4 6-2.
Elsewhere, three-time major champion Wawrinka beat Nishikori 6-4 6-4 and Kyrgios claimed a 7-6 (7-1) 0-6 6-3 victory against Borna Coric.
|Ludwigsburg stun high-flying Murcia in BCL|
|Rams v Chiefs moved to LA due to Mexico City field conditions|
|Skriniar discussing new Inter contract, confirms agent|
|Former Barcelona boss Martino named MLS Coach of the Year|
|Bell fails to report to Steelers, will sit out rest of season|
|Federer back on track after dismal Thiem display|
|Udinese appoint Nicola after sacking Velazquez|
|Monaco deny they broke rules regarding youth recruitment|
|Del Bosque, Zidane, Lopetegui - The former Castilla coaches Solari follows into Real Madrid hot seat|
|Ozil rejected ´crazy offers´ from Asia, reveals agent|
|Real Madrid appoint Solari on permanent basis|
|LeVert avoids need for surgery, should return this season|
|Neuer confident despite concerns over Bayern Munich form|
|All I ever wanted to do is win, says Sixers signing Butler|
|Pogba: Coming home to United was the best feeling ever|
|Watson among four signing new Bath deals|
|Susanna Dinnage to replace Scudamore as Premier League chief executive|
|Murray commits to Brighton until 2020|
|Rooney rejected chance of pre-World Cup farewell|
|Impressive Anderson thrashes Nishikori|
|Ozil´s Germany absence a ´pity´, says Sane|
|Rooney: I´ll finish my career in the US|
|McIlroy unsure of 2019 European Tour membership|
|Australian Open dismisses concerns of Federer scheduling bias|
|Hue Jackson joins Bengals staff as ´special assistant´|
|Real Madrid confirm Reguilon injury|
|Higuain handed two-match ban for Juve meltdown|
|Kruis ruled out for England as Jones calls up uncapped quartet|
|A year on from Italy failure, Ventura leaves Chievo after four games|
|Bairstow misses out as unchanged England promote Stokes|
|Recalled Alba denies Luis Enrique bust-up|
|´Unhappy´ Christensen won´t push for Chelsea exit|
|Nadal to make Abu Dhabi comeback in December|
|Taijul helps Bangladesh tighten their grip despite Taylor ton|
|Neymar joining Real Madrid wouldn´t hurt Iniesta|
|It´s just team spirit - Livingston not worried by Durant-Green exchange|
|Trippier out of England squad with groin injury|
|Ex-Sri Lanka international Lokuhettige charged by ICC|
|Former England and Chelsea star Joe Cole retires|
|Nets offer support to LeVert following serious leg injury|
|Panenka proud Sergio Ramos imitates his penalties|
|Liverpool´s Alisson seeks patience to reach potential|
|Anthony Davis leads Pelicans, Clippers hold off Warriors in OT|
|Lindelof rues international break for Man Utd|
|Shaqiri confident in more goals for Liverpool|
|Giants too good for 49ers in crunch time|
|Southgate named honorary Yorkshireman|
|Nicky Butt: Manchester United are low on confidence|
|Criticism of Barcelona star Dembele is overblown - agent|
|Thibodeau discusses Butler trade: We thought this was the best deal for us|
|Acuna, Ohtani win rookie of the year awards|
|LeBron James on Lakers’ early season struggles: ‘I almost cracked’|
|Welbeck has successful second operation on broken ankle|
|UEFA warns FFP cases can be reopened based on ´new information´|
|Foakes to keep England place for second Test|
|WATCH: Rooney looking sharp in England training return|
|Mbappe: Money in football is truly indecent|
|Djokovic back to brilliant best as Isner is beaten|
|Celta Vigo replace Mohamed with Cardoso after Real Madrid defeat|
|Joshua intrigued by Usyk, says Hearn|
|Ibrahimovic beats Rooney to MLS Newcomer award|
|Rams WR Kupp out for season with torn ACL|
|Sturridge denies ever gambling on football following FA charge|
|Koeman understands De Ligt´s Eredivisie frustrations|
|Jimmy Butler trade: 76ers acquire Timberwolves star in blockbuster deal|
|´Improve your attitude´ - Deschamps issues Dembele warning|
|Sturridge charged with misconduct over alleged breach of betting rules|
|Saints sign Marshall following Bryant injury|
|Mendy suffers knee injury, leaves France squad with Lacazette|
|Zverev beats Cilic in error-strewn London battle|