Pace just as crucial off the court as on

The height of the tennis season is the six weeks sandwiched by the French Open and Wimbledon, and that's when the players want to hit their heights, too.

After weeks of grinding it out on the red clay courts of Europe, the pros head into the biggest stamina test of the season in Paris, and then must recover in time to play Wimbledon two weeks later. It's no surprise that the players left standing on the weekends are the ones who have learned how to pace themselves.

It's a lesson even the likes of Rafael Nadal have to take to heart. This time last year, his knees were killing him, his mind was clouded over his parents' divorce, and he had played four out of five weeks during the buildup -- 19 matches in all, including a four-hour marathon against Novak Djokovic in the Madrid semifinals. When he ran into an in-form Robin Soderling in the fourth round of the French Open, the Spaniard's depleted reserves ran out.

That experience played a role in Nadal's decision to retire from his match against Andy Murray in the Australian Open at the beginning of the season. "I said, 'Well, I [won't] repeat the mistake of last year. I go to the limit, not cross the limit, no?'"

He has continued to follow that rule even during the clay-court season, when his superiority on the surface and a number of home tournaments mean the pressure to play is the greatest. This year, Nadal has taken one week off after each tournament he has played, winning all 15 matches and dropping just two sets. That meant skipping a favorite Spanish event in Barcelona, but the disciplined scheduling has paid off.

"I didn't have problems with my knees for a whole week. Unbelievable," he said after winning Rome. He arrived in Paris without any reports of problems.

In recent years, Federer has proved to be the master of managing his schedule, building in break periods throughout the season and paying careful attention to any aches or pains.

"I play in pain 80 percent of the time," Federer told sponsor Credit Suisse in a recent interview. "Something always hurts, but these pains often disappear again during the warm-up or can be massaged away by the physiotherapist. It is hugely important to know your body well and have a reliable early warning system.

"That's why the breaks in between tournaments are so important to me -- not just physically, but also mentally. The pressure of a tournament is as great off the court as it is on it."

This year's "What Not To Do" chapter was eloquently self-authored by Sam Querrey, who delivered a brutally frank assessment of his performance after a first-round loss at the French Open.

"Just tired. Not into it. Mentally not there," he said. "I started thinking about leaving and pulling out of the doubles and how much I wanted to go home, how much I wasn't enjoying … I've not been a professional on and off for the last few months. You're out there facing one opponent. I don't want to face the opponent and myself."

It was a disappointing end to a promising run that included a tournament victory in Belgrade and a final in Houston. Overall, however, Querrey's clay-court record looks like a wave chart, with the low points coinciding with the biggest tournament (although that's probably not coincidence).

"Those are 250 [-level events], and they're great … a tournament win is a tournament win," Querrey said. "But I won Belgrade and my ranking didn't move. I'm kind of past that point right now. Those 250s do nothing for me ranking-wise. It's all about the Masters Series and the Grand Slams."

His conqueror, Robby Ginepri, understood how he felt. "I kind of went through the same thing -- [we] took a bus here from Düsseldorf [last week]," he said. "We both played on Saturday, had to sit in a car for almost five hours, got here around, like, 1 a.m. on Sunday.

"It's not surprising. He's been over here a long time. I hope that he'll learn from this and realize that obviously this is one of the biggest tournaments. The four Grand Slams are definitely the ones that you need to be the freshest for, with it being three out of five [sets].

But it's not easy to find the right formula, said Andy Roddick, who finds himself at the other end of the spectrum, having played no clay matches ahead of the French Open after entering only Madrid and having to pull out with a stomach problem.

"It's tough for [Querrey] because when he's in the States he plays really well when he plays a lot. He can play a lot," Roddick said. "You learn. I feel like I have a better grasp on my schedule now than I did when I was 21 or 22, and it seems like I played everything."

The men's and women's tours also are sources of pressure, encouraging players to play more often, with carrots like bonus-pool money and penalties like zero-point ranking slots for missing a mandatory tournament. Smaller events also give top players appearance fees for playing.

Caroline Wozniacki takes all of this seriously. After injuring her ankle last month at Charleston, she took just one week off and then played four straight weeks coming into the French Open, never winning more than one match at any of those events.

"There are some rules on the WTA Tour, and we have to follow those rules," she said. "It's not just a fine. It's also commitment tournaments, zero-pointers. Yeah, some other things that plays in [your] mind."

As a result, it often takes a serious injury to get players to assess their limits and manage their schedules accordingly. Teenager Anastasia Pavlyuchenkova faced that question after suffering a stress fracture in her foot in April, and she has been more careful since.

"With me, I think I wasn't used to playing a lot of tournaments in a row," she said. "I won my first title [in Monterrey] -- a lot of emotions, it was something new, and then I played Indian Wells, Miami. It was a lot of tournaments in a row in the U.S.

"I think it was like a sign for me to stop playing so much and just go back to Moscow and rest and prepare for the clay-court season. So I think it was for the best, in a way.

"Of course, it's not always good to have an injury, but maybe for me it was good to stop and think."

Kamakshi Tandon is a freelance tennis writer for ESPN.com.