Federer was the three-time defending runner up of the French Open heading into 2009 at Roland Garros. His attempts at trying to capture the only grand slam he didnt own had repeatedly been denied by Nadal.
In the fourth round, Robin Soderling pulled off one the greatest upsets in tennis history in handing Nadal his first loss in Paris. That opened the door for Federer, but it certainly wasn't easy.
The day after Nadal went out, Tommy Haas had Federer on the ropes after winning the first two sets. Federer nearly went down a break late in the third set as well, but an amazing forehand saved him that and then he cruised from that point on.
In the semifinals, Federer was down two sets to one to Juan Martin del Potro before finishing that match strong as well.
The championship match was much different, however, as Federer played one of his best matches in his career to knock out Soderling in straight sets. After the final point, the Swiss Maestro was more emotional than I've ever seen him, as he knew the significance of the win.
The victory meant Federer had become the sixth men in tennis history to complete the career grand slam (winning each of the four majors at least once), just about completing his resume. He also tied Sampras' all-time record with 14 grand slam singles titles.