The Red Sox called up Nava prior to Thursday's game against the Indians, which caught the 29-year-old outfielder a bit off guard.
"I was definitely surprised," Nava said. "I'm happy, but shocked."
Nava had been playing down at Triple-A Pawtucket, hitting .316 with three home runs and 17 RBIs in 27 games. The outfielder spent time in Boston in 2010, during which he batted .242 with a home run and 26 RBIs in 161 at-bats. But even that taste of the big leagues didn't mean Nava was expecting Thursday's call-up, although he admits he's better prepared this time around.
"I've leanred a lot of things [since 2010]," Nava said before Thursday's game. "Learned a lot of things just how to handle yourself. Getting ready for a game. I think when I was called up, initially I was playing every day, and then when I got called up at the end I wasn't playing every day, learning how to adjust to coming off the bench. That was something that was new. I think that's going to help me as far as the opportunity. I'll be a little more prepared the second time around."
Nava said he's ready to take on whatever role manager Bobby Valentine needs him to, and on Thursday, that meant batting sixth and playing left field.
Valentine said the need for another left-handed bat led to the transaction.
