Rafael Nadal has all the tools in play to make him very tough to beat. He's such a good athlete and such a good defensive player, and you have to do so much to win a point against him.
I think Roger Federer feels that way, too. Nadal does to Federer what Federer does to other players -- that is, use his speed to force his opponent to hit one extra good shot. You have to go to such great lengths to win a point against Nadal, and ultimately players can't string those together.
Obviously, being left-handed helps Nadal against Federer (hitting his forehand into Federer's backhand). Other players don't find it nearly as easy to find the Federer backhand as Nadal does because he puts that heavy topspin forehand into Roger's backhand and gets it up high.
Nadal is also an efficient server, and he's very hard to break. He's going to put the ball in play to his opponent's backhand; he doesn't put a ton of pace on the serve, but he gets it in play. He doesn't allow you to attack his serve because he gets a high percentage in.
To beat Nadal, you have to break him. You have to hope Nadal has a day when his service percentage comes down enough that you can attack his serve.
On the clay in Rome, Federer came in a ton against Nadal and was volleying brilliantly. Sometimes it was enough to win the point and sometimes it wasn't. It's tough to play aggressively against Nadal unless you come in on great approach shots.
His security blanket is his defensive ability; Nadal makes his opponent work so hard to win every point that he just doesn't give up cheap points. Other players probably have more of a mental block about facing Nadal on clay than they do about facing Federer on grass, because they know it's going to be slow torture.
There are very few players -- if any, besides Federer -- who think they can beat Nadal on a clay court. His opponents speak of him in awe. You aren't going to outwork him; he's too fit and moves too well.
ESPN's Chris Fowler will provide analysis for ESPN.com during the French Open.