Nava's start on Sunday was his 24th in left field in the 24 games he's been back on the team.
The switch-hitter was hitting .315 with two homers, 18 RBIs, a .453 on-base percentage and a .534 slugging percentage entering Sunday.
Instead of sitting Nava, third baseman Will Middlebrooks was out of the lineup, as Adrian Gonzalez moved back to first base and Kevin Youkilis played the hot corner.
"I looked at [Nava] in the training room," Valentine said. "He's young, he's strong. He's feeling good. The last thing I think he needs is two days away from making good contact."