FOXBOROUGH, Mass. — Who’s on first?

Exactly.

The Abbott and Costello baseball comedy routine could easily describe the New England Patriots’ offensive line as the team prepares to play the Miami Dolphins on Sunday.

Who exactly will play? Who exactly will be responsible for keeping Tom Brady off his hindside?

With the stunning trade of left guard Logan Mankins – a six-time Pro Bowl selection – to Tampa Bay last week, the offensive line appears unsettled.

We know the tackles will be Nate Solder on the left and Sebastian Vollmer on the right (maybe). But who will play in the middle?

The first “unofficial depth chart” of the season listed Josh Kline, a second-year player with one start last year, at left guard, Ryan Wendell at center and Dan Connolly at right guard.

Of the three, Connolly, who was just elected a team captain, appears to be the one lock to start – at right guard or center, where he played in 2011. Otherwise? Kline looked OK against the Giants in the final preseason game but was bull-rushed badly a couple of times. Wendell is coming off what many feel was a very poor season.

The primary backups appear to be Jordan Devey, who played a lot at right guard in the preseason; Marcus Cannon, a fourth-year pro with considerable talent and versatility; and rookie center Bryan Stork.

Why do we care so much about the offensive line?

Because as Brady goes, so goes the offense. And keeping him off his back is the best way to get this offense, which can be explosive, moving.

Consider these facts:

In Brady’s two MVP seasons (2007 and 2010) he was sacked a combined 46 times. He also threw for 86 touchdowns (50 in 2007) and only 12 interceptions (four in 2010) in those two seasons.

Now let’s look at 2013, universally considered the most challenging of Brady’s career. Last year he was sacked 40 times – the second-most in his career, surpassed only by the 41 times he went down in 2001, his first starting season. Last year he threw for only 25 touchdowns, a drop of nine from 2012, and was intercepted 11 times.

That doesn’t include, of course, all the hurried throws he had to make because of constant pressure in his face.

The Mankins trade was the latest upheaval to a veteran crew. In the offseason Dante Scarnecchia retired after 30 years as an assistant with the team. He was the offensive line coach for the last 15 years and was regarded as one of the best in the game.

He was replaced by Dave DeGuglielmo. Then the Patriots drafted three offensive linemen, two of whom stuck: Stork and tackle Cameron Fleming.

The Patriots knew they had to get better and younger, and they did.

But trading Mankins is a risk, even for Bill Belichick, who has never been shy to cast off a veteran player. Even though his pass blocking had declined the last couple of years, Mankins was not only the team’s best offensive lineman but its toughest. He played an entire season with a torn ACL.

Someone has to step up and chances are we won’t know for a while who that will be. There were reports last week that Vollmer had been asked to play left guard. He – surprise – wouldn’t comment on those reports. But such a move could maybe get Cannon into the lineup, too.

If Brady is worried about his protection, he’s not showing it. He said in an interview on WEEI on Tuesday that while he will miss Mankins – “Nobody stood for Patriot football more than him” – it’s time to move on already.

He was asked Wednesday about his comfort level with this reshuffled group.

“All those guys are working hard to find a spot, find a role,” he said. “When the coaches make those decisions, then that means the players have to adapt. That’s kind of the way it is and has always been here. However it sorts itself out, all the guys are going to be prepared to play.”

We’ll find out quickly just how good this Patriot offensive line is.

The Dolphins’ defensive front is, said Belichick, “one of the best fronts, defensive lines, that we’ll see all year. They’re physical, they run well, they’re tough, use their hands well, they’re aware, big blocking schemes. They don’t really get fooled much. It’s good.”

And the five guys who line up on the Patriots’ offensive line – whoever they might be – better be ready. Otherwise the heat is really going to be on Sunday in Miami.