Roger Federer has continued his mastery over Stan Wawrinka, but not before getting a fright en route to a 6-7 (7-2) 7-6 (8-6) 6-2 quarter-final victory at the Cincinnati Masters.
Federer improved his career record against his Swiss compatriot to 21-3.
A match that started with a low key atmosphere developed into a cracking affair when Federer took the second set tiebreak.
While Federer narrowly avoided an early exit, another high seed was sent packing, as number four Juan Martin del Potro fell to Belgian David Goffin 7-6 (7-5) 7-6 (7-4).
His reward is a Saturday evening semi-final against Federer, while the other last four clash will match former world number one Novak Djokovic of Serbia against Croatia's Marin Cilic.
It was a busy day for 10th-seeded Djokovic, who came from behind to oust defending champion Grigor Dimitrov of Bulgaria 2-6 6-3 6-4 in the conclusion of a third round match carried over from Thursday.
Only a couple of hours later, Djokovic stopped Milos Raonic 7-5 4-6 6-3, improving his career record to a perfect 9-0 against the Canadian.
"I'm very pleased with my fighting spirit and staying mentally tough to overcome deficits in both matches," Djokovic said.
"Obviously the match against Dimitrov yesterday didn't start so well for me. He started tremendously well.
"And to go back on the court again against Raonic, who was serving 140-plus miles (per hour) from the first game, that got me going, for sure, from the beginning."
Former champion Cilic made his way to the semi-finals with a 7-6 (7-5) 3-6 6-4 third-round win over Russia's Karen Khachanov before toppling Spaniard Pablo Carreno Busta 7-6 (9-7) 6-4.
Earlier on Friday, in matches held over because of a rain delay, Federer outlasted Leonardo Mayer of Argentina 6-1 7-6 (8-6) in the third round.
Wawrinka beat Marton Fucsovics of Hungary 6-4 6-3 in their third-round match.
Fourth seed Del Potro overcame Australian Nick Kyrgios 7-6 (7-4) 6-7 (8-6) 6-2.
Goffin did not face a break point in defeating sixth seed Kevin Anderson of South Africa 6-2 6-4 in 76 minutes.
