BOSTON — We’ve seen a lot of strange Red Sox lineups this season. That’s what happens when you have 10 players on the disabled list, which is what Manager Bobby Valentine was dealing with until Ryan Sweeney returned to action Monday.

One thing we hadn’t seen — until yesterday — was Daniel Nava leading off. Nava was batting leadoff Monday for the first time in his major league career. His spot at the top of the order was further proof that he has won over Valentine.

“He has played so well,” said Valentine. “He’s got the best on-base percentage on the team during this short period. I was reluctant to do it earlier, I wanted him to get his feet wet at the major league level.”

Nava has been making the most of his return to the big leagues. He has drawn 13 walks this season, helping his OBP reach .431.

Only four Red Sox hitters have walked more — and each of them has played at least 10 games more than Nava.

But he is here because the Red Sox need outfielders. They had seven of them on the DL as of Sunday, and have gone through a dozen this season.

That’s how Nava got his second chance with the Sox, even though he never saw it coming. He spent all of 2011 with Pawtucket, and didn’t receive an invitation to big-league camp this year. That after getting 60 games with the big club in 2010, an appearance that began with a grand slam on the first pitch he saw.

This time, Nava is working to prove that first season in the bigs wasn’t a flash in the pan.

Nava 2.0 is a more mature, complete player who has clearly improved his defensive skill and is making the most of every at-bat.

On Saturday, Nava vowed to make the most of his ninth-inning opportunity after a poor decision earlier in the game. Nava tried in vain to throw out the speedy B.J. Upton, a decision that allowed the eventual go-ahead run to move into scoring position.

That run stood as the difference in a 2-1 game in the final inning. Nava drew a walk, and became the tying run that scored ahead of Saltalamacchia.

“Going into the last at-bat, I just wanted to put together a good at-bat because of that and knowing the situation of the game and probably being too aggressive and not thinking about who’s on third and stuff like that,” Nava said.

“Fortunately Salty got us the win, and that play kind of got erased but at the same sense, I’ve got to learn from that. That’s just huge, that’s just a defensive play which changes the output of the game. I gave him a big hug.”

There is no way to know where Nava will end up at the end of the season. Ryan Sweeney came back from the seven-day DL Monday and Darnell McDonald has been rehabbing in Pawtucket.

The Sox should eventually get the likes of Jacoby Ellsbury and Carl Crawford back from the injured list.

They will be a stronger team when they do, but role players like Nava will need to fight for playing time — or even a spot on the team.

If Nava continues to hit and get on base like he has, he will find a place to play. He doesn’t need to look far to see how things can work out for a player who works hard — his teammate, Darnell McDonald, went through 12 years of pro ball before he finally stuck with the Red Sox. He’s now with them for his third year.

And David Murphy was a player who showed great promise in Triple-A, but couldn’t crack Boston’s big-money starting lineup. He was eventually traded to Texas, where he has become a regular for the two-time AL pennant winners.

“(Nava) wasn’t on our radar when we got to spring training,” said Valentine. “We have been pleasantly, extremely surprised. And happy. He’s a great guy who knows what he can do. I like people who know what they can do.”

There’s nothing Nava can do about the health of other outfielders in the organization. All he can do is make the most of his opportunities. He has certainly done that.

Minor-league evaluators say Nava has learned to not waste time and energy worrying about his standing in the organization. That’s a level of maturity that will serve him well in the future.

If he is physically able to play, someone will find a place for him on a big-league roster.

So far, he has been playing an important role for a team that has been trying to survive in spite of an overwhelming number of injuries.

Tom Caron is the studio host for Red Sox broadcasts on the New England Sports Network. His column appears in the Press Herald on Tuesdays.