He wished for more.
The 23-year-old Spaniard feels his limitations every day during his comeback from two months off the tour to let his aching knees rest and heal.
Normally, he would have practiced another 45 minutes to get ready for his opening match this week at the USD 3 million Cincinnati Masters.
Now, he can't do it.
"I need to go slow, no?" he said, after the workout.
Going slow means not pushing too hard at his second tournament back on the tour. It means accepting that he won't be anywhere near his best when the US Open starts in two weeks.
"Sure, the US Open is very important," Nadal said, "but after the US Open remains a lot of the season, and I would like to be ready to play a good end of the season."
Nadal and Roger Federer, who have been nipping at each other's court-shoe heels for years, were two of the biggest uncertainties when the Western & Southern Financial Group Masters got started Monday with the top players practicing and resting. The highest-seeded player in action was No 9 Gilles Simon, who beat Wayne Odesnik 6-3, 6-2.

Sixth-seeded Juan Martin del Potro of Argentina withdrew from the tournament yesterday, saying he was tired after reaching the finals in Montreal over the weekend.
While Nadal takes it slow in his comeback from tendinitis in both knees, Federer is getting adjusted to life on the tour with twins in tow.
After he beat Andy Roddick in a record-length fifth set at Wimbledon for an unprecedented 15th Grand Slam title, Federer took some time off for fatherhood. His wife, Mirka, gave birth to twin girls on July 23. He was back on court last week in Montreal, where his family accompanied him. Like Nadal, he lost in the quarterfinals.
It wasn't for a lack of rest.
"I've been sleeping enough," Federer said yesterday, after his practice. "It's not been bad like I sort of expected. But, no, things have changed in a good way. I love my life now."
In a sense, it feels like old times.
With the two of them back on court, the top of the men's field is intact, if a little out of its customary order. Andy Murray's title in Montreal on Sunday nudged him ahead of Nadal for the No 2 spot when the new rankings were released yesterday, right behind Federer. It's the first time that Murray has been ranked among the top two.
Nadal's absence made it possible, which is why it didn't bother the Spaniard.

"It's only a number," he said yesterday. "I hope to be ready in the future to come back to No 2 or to be in the top position."
He broke into a grin.
"No 3 is a very good number, too," Nadal said.
Given how his year has gone, it's very good, indeed.
Nadal ended last year with the top ranking and got off to a good start this year before chronic soreness in his knees limited him during the French Open and forced him to miss Wimbledon. Federer regained the No 1 ranking while Nadal was away.
Back on court, Nadal has a lot of energy to work with and a lot of rust to work off.
"Fresher, sure," he said. "I don't know if this fresh is very good, but I'm fresher."
So is Federer, who is glad to have Nadal back in the bracket.
"Andy (Murray) and myself have both benefited from Rafa being injured," Federer said. "We both took advantage of it.
"Now, he's back, I'm back playing again after a few weeks. Everybody seems healthy again, and that can only be a good thing for the rest of the season."
The 28-year-old Swiss star is intrigued by how he does this week in Cincinnati, where he's won two titles and had some of his worst moments.
"This tournament has been tricky for me," he said. "I hope it's one of those years where I can go all the way again. I feel my game is good enough to do really well here."