There is a lot of mystery surrounding the 2013 tennis season. The match between Roger Federer and Rafael Nadal will be very telling.
The two former-No. 1 players will face each other in the quarterfinals of the ATP BNP Paribas Open at Indian Wells. That is not a typo; these two stars will really play in a tournament before the semifinals.
That is what happens when Nadal misses seven months of play due to a knee injury. The Spanish star dropped to No. 5 in the world rankings and is forced to face one of the top players early in the tournament, depending on the draws.
Since returning at the beginning of February, however, Nadal has played very well. He lost to Horacio Zeballos in the finals of his first tournament back, but since then has won 12 straight individual matches.
Although he started out with weaker competition, he has since built up to the higher levels. In his last tournament in Acapulco, Nadal dominated both Nicolas Almagro and David Ferrer, beating each in straight sets.
With the French Open coming up soon, it appears that the seven-time champion will contend for one more this year.
However, he has not faced Federer, he has not faced Novak Djokovic and he has not faced Andy Murray. There is a big gap between the top three and the rest of the world, and Nadal has to prove that he is truly back by competing tough with this group.
Similarly, Federer has also started his season with question marks. The 31-year-old player has not dealt with injuries, but it is clear that he is starting to lose a step in his age.
He has not won a tournament in 2013 in three tries, losing to Murray, Tomas Berdych and Julien Benneteau. While the Swiss star is still No. 2 in the world, it is obvious that he is not playing his best at this moment.
Then again, this is a veteran who has spent plenty of time in his career playing in high-profile matches. It is possible that he was not giving his full effort in the early rounds of these non-major tournaments.
We will know if that is true in his match against Nadal. These two rivals know that they cannot win without giving 100 percent on every volley of the match.
Finally, both players must show that they have the endurance necessary to compete in a Grand Slam tournament. Between Federer's age and Nadal's injury, the end of a long match could get very interesting.
Both players are coming off long matches in the fourth round that went three sets. The ability to get back onto the court and perform well will be very telling.
Whoever wins this match should feel confident going into the rest of the season. The loser will have some serious questions to answer.
Obviously, this is only one match, but it is as big of an event as you will see in the quarterfinals of a March tournament.