At Triple-A Pawtucket last season, Nava hit .268. This year he was hitting .310.
"I tried to learn from what happened last year," Nava said. "I really struggled out of the gate in Pawtucket, put a lot of pressure on myself and was pressing, and now I try to do the exact opposite -- just relax and I'm grateful for the opportunities I have."
Defense gained an added emphasis for Nava in Spring Training of 2011, a year he was invited to big league camp.
With Nava, a switch-hitter, playing well, others could lose playing time. On Saturday, for the first time since joining the Red Sox on April 23, outfielder Marlon Byrd was not in the lineup for a second consecutive game. Byrd has a five-game hitting streak.
Asked before the game about the lineup and if there were any health concerns that might be keeping him out, Byrd turned his back and did not reply.
Valentine said before batting practice that he had not had a discussion with Byrd.
"I didn't see him yet," Valentine said. "I went out for the early hitting and he wasn't out there."
Asked about Byrd's defense on Thursday, Valentine said, "He's gotten really good jumps on a lot of balls."
Offensively, Byrd has a .281 average with a .299 on-base percentage in 17 games with the Sox.
"On one ball hit over his head, I thought he did [take a wrong first step] straight back, but I thought he got to it," Valentine said. "And then the ball missed his glove. I'm not sure what to attribute that to. He's playing very hard, though, he's giving us everything he has."