In short, the Maestro needs to at least reach the semifinals of the Roland Garros to find a rhythm for this season.
Prior to the Rome Masters, he bowed out in Round 3 of Madrid to Japan's Kei Nishikori, fell to Nadal in the Indian Wells quarterfinals and Tomas Berdych in Dubai's semifinals. Thus far in 2013, Federer's best victory is over Jo-Wilfried Tsonga—who currently ranks No. 8—at the Australian Open.
Combine his recent early exits, two losses to Nadal and only one finals appearance, and it becomes clear that Federer must get back on track in France.
With Nadal ranked No. 4—not to mention the French Open being his best tournament—the Swiss is at risk of slipping further down the rankings. As Jon Wertheim of Sports Illustrated wrote on Monday, Federer might as well be lumped into the pool of of players fighting for second place:
Novak Djokovic—whom most would have picked to win the event not long ago—is suddenly backsliding. Murray might well miss the event because of a back injury. Federer is looking decidedly mortal on clay. And David Ferrer threatens Nadal the way Bing threatens Google.
That said, Djokovic at least defeated Nadal on clay this year; the two squared off in Monaco and Djokovic won in straight sets.
Regardless of his draw, Federer needs to make a deep run. According to Tennis Connected, this is the first year in over a decade where Federer has no victories before the Roland Garros:
Other challengers he must also be concerned with are Berdych and David Ferrer.
Previously mentioned was Berdych's win over Federer in Dubai. Berdych also enters France with impressive victories in recent tournaments, as he upset Andy Murray in Madrid's quarterfinals and then Djokovic in Italy.
As for Ferrer, he has given Nadal a tough match in their previous two meetings and took Murray to three sets in Miami's final.
Although Federer definitely still possesses the talent to fend off anyone but Nadal on clay, failing to build on Italy's finals appearance won't bode well regarding Wimbledon. Despite that having been his best tournament, Federer's recent roller-coaster play must get smoothed out with consistency.
Otherwise, he'll gradually slip as the season progresses.