After a career of mostly ups and precious few downs, Bernard Tomic is in danger of dipping outside the top 50.
Tomic's 6-2 6-3 second-round loss to defending champion Novak Djokovic at the Toronto Masters was the Australian teenager's eighth defeat from his past nine matches since the French Open.
In eight weeks, Tomic has slipped from a career-high No.27 in the world to 49th and also lost his all-important status as a grand slam seed.
Unless he does something big at next week's Cincinnati Masters, the 2011 Wimbledon quarterfinalist will be at the mercy of the draw at the US Open, starting on August 27.
His slide will leave Tomic with no protection against the top 32 seeds in the first two rounds at Flushing Meadows.
In his first match since losing to Andy Murray in the Olympic semifinals, Djokovic proved too strong for Tomic.
He claimed three match points with his sixth ace and clinched victory on the first.
"For the first match it was a decent performance," said the world No.2 and reigning US Open champion.
"Obviously at the start we played very long opening four games and I was struggling to find the rhythm, as most of the players who came in late from London did."
Murray also avoided post-Games let-down, Scotland's gold medallist toughing out a painful 6-1 6-3 win over Italian Flavio Cipolla.
Murray, who only arrived in Canada on Tuesday, took to the hard court with minimal preparation but pulled off the win in just under 90 minutes thanks to some help from the ATP trainers.
The world No.4 was treated on his left knee after breaking Cipolla for 3-2 in the second set. Murray was then constantly flexing the knee on his way to victory.
Meanwhile, Samantha Stosur opened her American hardcourt campaign with a much-needed victory at the WTA event in Montreal.
After a first-round bye, Australia’s reigning US Open champion was leading Simona Halep 7-5 4-4 when the Romanian retired injured.
The win was only Stosur’s second since reaching the French Open semi-finals in June on clay.
The world No.5 endured a disappointing grasscourt season with a second-round exit at Wimbledon and first-round loss at the London Olympics.Fourth-seeded Stosur next faces Czech Lucie Safarova for a place in the quarter-finals as she tries to rebuild her form and confidence before beginning her US Open title defence in two weeks.