Bob and Mike Bryan opened their quest for a fifth US Open crown and their 100th overall title together with a 6-2, 6-3 first-round victory Wednesday over Max Mirnyi and Mikhail Youzhny.
Novak Djokovic had a ragged start in the one tournament that has always eluded him.
Roger Federer rolled to a 6-2, 6-0 victory over wild card Peter Polansky in the second round of the Rogers Cup, and Stan Wawrinka, Ernests Gulbis and Richard Gasquet also advanced in the U.S. Open tuneup on Tuesday.
Robin Haase advanced to the semifinals of the Swiss Open by beating defending champion Mikhail Youzhny 3-6, 6-1, 6-4 Friday in a rematch of last year's final.
Top-seeded Mikhail Youzhny began his Swiss Open title defense by beating Kenny De Schepper of France 6-3, 6-4 in a second-round match on Thursday.
Two-time champion Thomaz Bellucci won his first-round match at the Swiss Open on Tuesday, beating Gerald Melzer of Austria 6-3, 6-4.
The 17-year-old Alexander Zverev reached the semifinals of his hometown tournament by defeating Tobias Kamke 0-6, 7-5, 6-3 in the Hamburg Open on Friday.
Serbian qualifier Filip Krajinovic defeated defending champion Fabio Fognini 6-4, 6-0 Wednesday as a host of seeded players crashed out in the second round of the Hamburg Open.
Dominic Thiem fought from 5-2 down in the final set and held off a match point before upsetting the eighth-seeded Marcel Granollers 2-6, 6-3, 7-5 in the second round of the Hamburg Open on Tuesday.
Roberto Bautista Agut defeated Lukas Rosol 6-3, 4-6, 6-2 in the Mercedes Cup final on Sunday for his second career title.
Roberto Bautista Agut and Lukas Rosol reached the final of the Mercedes Cup with victories over the top two seeds in the semifinals on Saturday.
Defending champion Fabio Fognini eased into the semifinals of the Mercedes Cup on Friday with a 6-4, 6-3 victory over Colombia's Santiago Giraldo.
Fabio Fognini opened the defense of his Mercedes Cup title by defeating Andrey Golubev 6-4, 6-4 to advance to the quarterfinals on Thursday.
Andrey Golubev defeated German wild card Philipp Petzschner 6-4, 6-1 to set up a second-round clash with defending champion Fabio Fognini at the Mercedes Cup on Monday.
The fifth-seeded Richard Gasquet and sixth-seeded Mikhail Youzhny crashed out in the first round of the Gerry Weber Open on Tuesday.
Serena Williams lost in the second round of the French Open on Wednesday, her earliest exit at a major tournament since falling in the first round at Roland Garros two years ago.