Chasing a shot, Roger Federer caught his right shoe in the French Open's red clay, twisting that foot awkwardly and tumbling to the ground.
Soon enough, he was in a real rut, in danger of his earliest exit from a Grand Slam tournament in nine years.
Federer regrouped and restored order eventually, coming back from a two-sets-to-one deficit to beat 15th-seeded Gilles Simon of France 6-1, 4-6, 2-6, 6-2, 6-3 on Sunday in the fourth round to reach his 36th consecutive major quarter-final.
During a rare stretch of mid-match mediocrity from the owner of a record 17 Grand Slam championships - the 2009 French Open trophy is part of his collection - Federer lost 10 of 13 games, including the one in which he fell.
But Simon, a former member of the top 10, could not keep Federer down.
On a roll
From 2-2 in the fourth set, Federer won seven consecutive games, taking that set and a 3-0 lead in the fifth. That was pretty much that, although the final game sure was tense. Simon held two break points that would have allowed him to get back on serve at 5-4, but Federer erased one with a service winner, the other with a big serve that set up a putaway.
After missing a forehand on his first match point, Federer converted the second when Simon pushed a backhand wide on a 10-stroke exchange.
Federer held his racket over his head in triumph, then swatted a ball into the upper deck. When they met at the net, Simon extended his hand for a shake - and Federer pulled him in for an embrace.
The victory was Federer's 58th in his French Open career, against 13 losses, equalling the mark for most tournament wins held by Guillermo Vilas and Nicola Pietrangeli. It also was Federer's 900th career win anywhere, which puts him fourth in men's tour history, behind only Jimmy Connors, Ivan Lendl and Vilas.
This one must rank among the toughest.
It came in the same stadium where Federer's streak of 23 Grand Slam semi-finals in a row ended with a loss in the 2010 French Open quarterfinals to Robin Soderling (who happens to be the only man to beat Rafael Nadal at Roland Garros).
Federer's major quarterfinal run, a record in the 45-year Open era, began at Wimbledon in 2004, shortly after he lost in the third round of the French Open to three-time titlist Gustavo Kuerten.
That streak sure seemed safe after a strong first set against Simon. But running after a ball in his backhand corner while ahead 3-2 in the second, Federer landed hard on his right knee as he fell when his right sneaker's toe stuck in the clay. Federer rose quickly, caked dirt running the length of his right leg.
Simon's shot there made the score 3-all. Appearing shaken, Federer double-faulted to begin the next game, then was broken when he sailed a forehand far beyond the baseline. That 4-3 edge gave Simon some real momentum, while Federer started to miss shots he was handling without a problem earlier in the match.
That second set against Simon was the first Federer had lost all tournament. And then Federer was broken at love to trail 3-2 in the third set, which Simon soon won.
A measure of Federer's popularity around these parts: As the fourth set began, thousands of fans joined in a chorus of support not for the Frenchman trying to pull off the upset, but his opponent. ``Ro-ger! Ro-ger!'' they cried, trying to will Federer to perform better.
Until then, Simon had heard his fair share of support, too, with chants of his nickname ringing out around Court Philippe Chatrier - "Gil-lou! Gil-lou!''
The first sign of a comeback came when Federer grabbed a 4-2 lead in the fourth set by breaking with a big forehand that forced an error by an on-the-run Simon. Federer let out a guttural yell and shook his racket. The fans roared.
They were even louder moments later when Federer held for 5-2 with a volley winner. And the crescendo kept building, especially when Simon put a backhand into the net, giving the fourth set to Federer.