German Florian Mayer defeated Bernard Tomic 5-7, 6-3, 6-3 on Monday, ending the Australian's chances of playing top seed Novak Djokovic at the Montreal Masters.
Tomic, who was knocked out in the second round of the Washington tournament last week by eventual champion Juan Martin del Potro, complained of windy conditions but was more upset with his own lack of initiative after winning the opening set of the first-round encounter.
He will now have to hit the practice courts after missing a chance to build up some valuable hardcourt experience before the start of the US Open in three weeks.
Qualifier Marinko Matosevic produced some good news for Australia by following up his defeat of Canadian Milos Raonic last week in Washington with a 6-2, 6-3 victory against Germany's Benjamin Becker.
Jesse Levine earned the first Canadian win of the week as he beat Belgian Xavier Malisse 6-4, 7-6 (7/4) to book a clash with Rafael Nadal.
Spain's Nadal will be playing for the first time in six weeks, when he was toppled in the first round at Wimbledon.
Japan's Kei Nishikori, seeded ninth, ended the hopes of another Canadian, downing Peter Polansky 4-6, 6-4, 6-2.
A run of poor form continued for Janko Tipsarevic and the 16th seed was defeated by Uzbek Denis Istomin 6-4, 6-3.
Croatian Ivan Dodig beat Grega Zemlja of Slovenia 6-1, 6-1 to set up a meeting with del Potro
Andreas Seppi of Italy needed three sets to get past Czech Lukas Rosol 6-4, 4-6, 7-6 (7/4). Latvia's streaky Ernests Gulbis found his game to dispatch Feliciano Lopez 7-6 (7/4), 6-4. Brazil's Thomaz Bellucci lost his fifth match in a row dating back a month, going down to Martin Klizan 5-7, 6-4, 7-6 (8/6).
Australian number one Tomic, ranked 41st in the world, got off to a good start but could not maintain his form against the experienced Mayer.
"I was up 5-2 in the first set and should have closed it out in the second," he said. "In the second set I didn't start that well. My concentration dropped and he played well."
Tomic managed only two aces and lost his serve four times.
"Florian is one of those guys who plays well once he gets his nose ahead," he said.
"In the first set he was tight but in the second I missed my opportunities and didn't focus very well -- he took over then."
World number one Djokovic has beaten Mayer in all five of their meetings, including the first round of Wimbledon in June.