Roger Federer needed less than an hour to defeat Canadian Peter Polansky 6-2, 6-1 at the Rogers Cup in Montreal on Wednesday in his first appearance since winning a record eighth Wimbledon title in July.
Gael Monfils produced the comeback of the day to beat Kei Nishikori in three sets while Canada's Denis Shapovalov enjoyed the biggest win of his young career by defeating hard-hitting Argentine Juan Martin del Potro 6-3, 7-6(4).
A day after celebrating his 36th birthday, Federer played the aggressive game that has propelled him to five titles, including two grand slams, this year, attacking the net and rocketing second serves.
Polansky never looked comfortable after he double faulted twice in his first service game and had difficulty handling Federer's pinpoint serves.
Federer, who has lost only two of 34 matches this year, will next play Spain's David Ferrer who prevailed in a three-setter against American Jack Sock 7-6(7), 3-6, 6-1.
Rafael Nadal enjoyed an easy rout of Croatia's Borna Coric as he raced through the first set in just 29 minutes and did not face a break point until the 13th game.
"At the beginning of the match there were great points. I think I started playing so well in the first set and in general, I played a great match" Nadal told reporters of the 6-1, 6-2 win.
"Last time that I played against him I lost, last year in Cincinnati. It was not an easy round for me."
Nadal will next face the 18-year-old Shapovalov who pumped his fists and rose his arms in triumph after dispatching the 2009 US Open champion, who struggled with the accuracy of his serve during big moments in the match.
A Del Potro double fault put Shapovalov up a break at 6-5 in the second set, but nerves appeared to get to the tournament wildcard, who needed a tie-break to prevail.
Monfils, however, fended off four match points to beat Japanese world number nine Nishikori in a three-set thriller 6-7(4), 7-5, 7-6(6).
The 27-year-old Nishikori had two chances to serve out the match and led 6-2 in the decisive tiebreak, before Monfils won six successive points to complete a superb fightback.
He will face Spaniard Roberto Bautista Agut in the third round.
Fourth seed Alexander Zverez and seventh seed Grigor Dimitrov each needed three sets to advance while ninth seed David Goffin was upset by South Korean Hyeon Chung 7-5, 6-3.
Sixth seed Milos Raonic was also upset by Adrian Mannarino 6-4 6-4 while American Sam Querrey beat France's Jo-Wilfried Tsonga 6-1, 3-6, 6-4.
Pliskova begins number one reign with ragged win, Mugaruza tames Flipkens
Karolina Pliskova began her reign as world number one with a ragged 6-3, 6-3 second round win over Anastasia Pavlyuchenkova on a blockbuster Wednesday when eight of the top 10 ranked players are in action at the Rogers Cup.
Pliskova, playing in her first tournament since her shock second round defeat at Wimbledon, struggled with a misfiring first serve and was guilty of some lapses in concentration. However, the lanky Czech was never seriously threatened as she disposed her 19th ranked Russian opponent in a tidy 70 minutes.
"I had a little bit (of nerves) before the match but during the match I felt much better especially at the end," Pliskova said in a courtside interview.
"I think it was not the best tennis from my side but I was trying to improve in the match.
"I'm definitely happy I am through to the next round, the first match is always tough."
Both sets followed a similar pattern, Pliskova surging to a 5-1 lead in the first and 3-0 in second. A loss of focus allowed Pavlyuchenkova to break and hold serve to trim the deficits.
But Pliskova snapped out of her brief funks each time and clinched her first win as number one with her seventh break.
A star-studded day on centre court began with Wimbledon champion Garbine Muguruza taming Belgian qualifier Kirsten Flipkens 7-5, 6-2.
Despite a lowly ranking of 82nd, Flipkens represented a tricky first test for Muguruza with the Spaniard holding a slight 3-2 edge in their head-to-head meetings.
Muguruza, who had won only one match in her two previous visits to the Canadian hardcourt event, was tested during a topsy turvy opening set and served for the first set at 5-4 before double faulting to hand Flipkens a break.
The world number four hit back with a break of her own and then held serve to clinch the opening set, despite 30 unforced errors.
Muguruza looked much more like the player who dropped only one set on her way to the Wimbledon title after that and collected the early break in the second set to take control of the contest.
The Spaniard will now cross swords with Ashleigh Barty of Australia for a place in the last eight.
Seven-time Grand Slam champion Venus Williams produced a rich vein of form as she overcame in-form Ericsson Open champion Katerina Siniakova of Czech Republic to reach the third round of the Rogers Cup in Montreal on Thursday.
The 37-year-old, who finished as the runner-up in Montreal three years ago, was forced to draw on all of her vast experience before she eventually prevailed Siniakova 7-5, 7-5 in an exhilarating second-round clash that lasted for one hour and 39 minutes.
Williams snapped Siniakova's six-match winning streak in style as she hammered 32 winners, including 12 aces, while making just nine unforced errors throughout the two-set thriller.
With the win, the American has now set up a highly-anticipated pre-quarterfinal clash against No. 5 seed Elina Svitolina, who defeated Russia's Daria Kasatkina 7-6, 6-4.
Williams, who will be chasing her third US Open crown next month after reaching the Wimbledon and Australian Open finals this year, had earlier registered her first-ever win in Toronto when she rebounded strongly to post a 6-1, 3-6, 6-3 win over Irina-Camelia Begu in a rain-hit opening encounter.
American teenager Catherine Bellis continued her brilliant form on the North American hardcourts by taking down eighth seeded Russian Svetlana Kuznetsova 6-4 7-5 to reach the third round.
The 18-year-old arrived in Toronto after reaching the semi-finals in Stanford last week.
Kuznetsova was joined at the exit by her 16th seeded compatriot Elena Vesnina, who suffered a shock 6-3, 5-7, 6-4 loss to Australian qualifier Ashleigh Barty while Czech Lucie Safarova provided another upset by stopping 11th seeded Dominika Cibulkova 6-2, 6-4.
Murray withdraws from Cincinnati Masters, eyes US Open return
World number one Andy Murray will not compete in the Cincinnati Masters next week due to an ongoing hip injury, but hopes to play at the US Open in New York later this month, he said on Wednesday.
"Unfortunately I won't be playing in Cincinnati as I continue my recovery," Murray said in a statement.
"I always enjoy playing there and I look forward to returning next year. I'm continuing to work hard on the court with the aim of being in New York."
Murray's decision has hampered his hopes of winning a second US Open title as he has yet to play in any hardcourt tournaments in the lead up to the final major of the year.
He has been out of action since losing in the quarter-finals of Wimbledon in July.
The 30-year-old Briton has held the number one ranking since November of last year, but that may not last much longer.
Murray's absence at the Rogers Cup in Montreal this week means Rafael Nadal could take the top spot should the Spaniard advance to the semi-finals in Canada.