Roger Federer is no longer the top tennis player on the planet, we know that much.
But what will we learn in Paris this summer?
At age 31, the 17-time Grand Slam champion is struggling to keep pace with the elite players in the men's game. If you disagree, take a look at the numbers.
Nearly five months into the tennis season, Fed is just 18-6 in singles play and has yet to win a single tournament. Not since 2000 has Fed begun the year with such a lengthy drought.
That's why the 2013 French Open this summer in Roland Garros will be the most telling Slam appearance of Fed's career. A French Open champion in 2009 and a five-time finalist in Paris, the Swiss legend has experienced tremendous success at the year's second major tournament despite winning just once in 14 tries.
If Federer's brilliant performance at Wimbledon last summer reminded us that he was still among the game's top players, this year's French Open run could reveal whether Fed is primed to repeat at the All England Club in 2013 or set to stumble down the stretch before turning 32 in August.
It's no secret that tennis players begin to fade as they age, especially after they reach age 30.
Despite having played 1,100 singles matches over the course of his career, Fed has still been a model of consistency at Grand Slam tournaments. After all, he's played in and reached the quarterfinals at every major dating back to the 2004 Wimbledon Championships.
But what if Fed gets knocked out in the fourth round in Paris this summer?
Eventually we'll have to acknowledge that Fed is no longer on the same level as the other three members of the Big Four—because he's not.
In 2013, Fed is 0-3 against Andy Murray and Rafael Nadal. He's yet to play world No. 1 Novak Djokovic this season, but he's won just two of his past seven meetings with the top-ranked Serb, dating back to the 2011 U.S. Open.
If a short French Open run wouldn't convince you that Fed is fading from the elite, consider the following: Fed is just 2-5 against Djokovic in their last seven meetings, 1-3 against Murray in their last four meetings and 4-12 against Nadal in their last 16 matchups.
While those marks would be considered impressive for any other player in the ATP Top 10, they are telling for a legend like Federer, who was once untouchable and a lock to make the French Open final, even if Nadal was the man to beat.
Now, having failed to reach the final at Roland Garros in two of the past three years, Fed is set to embark on the most revealing Grand Slam journey of his career in 2013.
At this stage of Federer's season and at this point in his career, an early exit or run to the final would not only be significant, but telling in terms of what Fed's future holds.
Follow Bleacher Report Featured Columnist Patrick Clarke on Twitter.
Like the new article format? Send us feedback!