World number two Roger Federer, bidding for his eighth Cincinnati Masters title, outlasted Leonardo Mayer of Argentina 6-1 7-6(6) in the third round on Friday.
Playing in his first tournament since Wimbledon, Swiss Federer lost just four first-serve points and did not face a break point in the match.
Mayer had a chance to force a third set, but Federer held on to win his third consecutive meeting with the Argentine as players double up in matches in the rain-delayed tournament.
Federer will face compatriot Stan Wawrinka in the quarter-finals later on Friday.
Wawrinka beat Marton Fucsovics of Hungary 6-4 6-3 in their third-round match.
“It’s been a while since I’ve played two matches in one day. Apparently it was 2004,” Federer told ESPN. “I did play a lot of practice twice a day so if I won’t be ready for today, I’ll never be ready.
“Playing against Stan obviously is a treat. Ten years ago and two days ago we won the Olympic gold together and we’re still playing… I’m very excited to play against him and it’s great for him, I’m happy to see him back again.”
Mayer’s compatriot Juan Martin del Potro and Serb Novak Djokovic also advanced.
Fourth seed Del Potro overcame Australian Nick Kyrgios 7-6(4) 6-7(6) 6-2 and former world number one Djokovic, the 10th seed, ousted defending champion Grigor Dimitrov of Bulgaria 2-6 6-3 6-4.
Del Potro will play Belgian David Goffin in the quarter-finals.
Goffin did not face a break point in defeating sixth seed Kevin Anderson of South Africa 6-2 6-4 in 76 minutes.
Djokovic returned to the court after rain halted play on Thursday with a break lead in the third set and completed the win.
He will take on Canadian Milos Raonic in the quarter-finals, also on Friday.
Former Cincinnati champion Marin Cilic survived a rain-delayed three-setter, the Croatian battling past Toronto semi-finalist Karen Khachanov 7-6(5) 3-6 6-4.