Fitness is what is holding back Jack Sock

A couple things were clear in the past week with Jack Sock's stints in Stockholm and Basel:

1. He's ridiculously loaded with talent
2. Fitness is still holding him back

The young American phenom that possesses a nice serve and a huge ground game with a heavy forehand and a decent ability to grind for his big size. He has all the tools to be successful in this modern game, even with slower balls and slower courts. It's funny, I look at a guy like Steve Johnson who has a huge serve and a big flat forehand and I feel like he's got no shot to progress because he has no backhand and no grinding ability. The courts are too slow for him these days. Johnson would have been a good ATP player in the 90s. Even though his forehand is huge, it's flat and the margins are small. Not Sock. Sock has tons of action and a lot more margin on his shots, and when he's not playing well he can play a little defense and grind. His assets can get him to the top of the game.

So what's holding Jack Sock back? You'll notice he put on a ton of weight when working out with Agassi and Gil Reyes in Vegas last year. The idea was to load up on calories and gain a bunch of weight that he could then turn into power. As he's trimmed down a good bit since then it seems the Agassi camp gave him a good baseline of strength. Endurance and cardio remain a question mark, though.

In Stockholm, Sock took out a listless Bernand Tomic 6-4, 6-2 before losing to David Ferrer 6-4, 3-6, 1-6. Now one 6-4 set with Ferrer will take a more significant physical toll on one's body than a lot of two long sets against other opponents. But there is no denying Sock faded down in the stretch.

In Basel this week Sock wasn't playing nearly as well but still managed to grind out an impressive 7-6, 4-6, 7-6 win over Stephane Bohli in quallies. He then collapsed in the qualifying round against Tobias Kamke, 0-6, 4-6.

So Sock has the game and ability to compete. He beat Tomic and took it to Ferrer for over a set. Even the win over Bohli, a much weaker opponent, was impressive as he showed the ability to stay the course when not playing as well. What was disappointing was how quickly he faded fitness wise against Ferrer, and in the match after the Bohli win. Ultimately the ATP tour isn't about potential, it's about recovery. Winning one round is great and all, but how quickly can you get yourself ready to show the same physical effort for the next one? That's why Smyczek is climbing up the rankings - he's adopted the Mike Russell school of giving the same exact effort each time out. We're not seeing that from Sock yet.

This offseason will be critical for Sock. He needs to have the endurance and fitness to string several matches together. That is the last remaining hurdle to him getting in the top 40 rather quickly.