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9/21/2013 8:25 P.M. ET

Middlebrooks makes debut as first baseman

BOSTON -- Will Middlebrooks made 153 of his first 154 career Major League starts at third base. He was the designated hitter once.

Until Saturday night, when Middlebrooks got his first career start at first base against the Blue Jays, a position he had never played before, at any level. He had worked out there a few times this week. Middlebrooks doesn't own a first baseman's glove and had to borrow Mike Napoli's.

But Middlebrooks is an athlete, according to manager John Farrell. And with the American League East title in hand, adding defensive versatility was too good of an idea to pass up.

"There may be the potential of a situation in the postseason where if we pinch-run for Nap, does [Middlebrooks] go over to first?" Farrell said.

If the Red Sox advance to the World Series and need to double-switch at a National League park, the versatility would be especially useful.

"This is a good time to feel it out and get used to it," Middlebrooks said. "It's not too hard, I don't think. The ball in between me and the pitcher and second base is the one I really have to get the feel for. The balls curve the opposite way as third base. It's glove side. I shouldn't have to go back there as much. I'm not too worried about it. I'm trying not to overthink it."

Farrell said the most difficult part of the transition is identifying which balls are worth going after and which Middlebrooks should let go and retreat to cover the bag.

"But again, he's an infielder, he's required to do some things [that are] reactionary and that's going to be the same at first base," Farrell said.

Ellsbury is likely to return in regular season

BOSTON -- Red Sox outfielder Jacoby Ellsbury, who has been sidelined with a foot injury, is still on track to return to the lineup before the last regular-season game against the Orioles on Sept. 29.

Ellsbury did some running, throwing and hitting on Saturday. He might take batting practice prior to Sunday's series finale with the Blue Jays.

So what are the Red Sox waiting for?

"Probably the first-step quickness, the explosiveness either in a stolen base or getting a read on a route in the outfield," manager John Farrell said.

Ellsbury hasn't played since Sept. 5. If he returns by the last regular-season game, he'll have needed less than a month to recover from a compression fracture in his right foot.

"He's making steady progress," Farrell said. "We're hopeful that he'll be back in our lineup sometime in this coming trip."

Red Sox trying to rest in push for home field

BOSTON -- With the American League East title in hand, the Red Sox rested Dustin Pedroia, Mike Napoli, Jarrod Saltalamacchia and Mike Carp for Saturday night's game against the Blue Jays.

Manager John Farrell said he's not downplaying the importance of home-field advantage in the playoffs, but the Red Sox entered Saturday with a 94-61 record, providing enough of a cushion between them and the Oakland A's, who had the second-best record in the AL at 91-63.

The Red Sox still want to win, but they're being smart about providing rest when necessary. Pedroia had played in 154 of the team's 155 games before Saturday. Saltalamacchia had caught 974 innings behind the plate.

"We do have a number of things we have to balance in that, and that's some individual things we have to manage with some guys," Farrell said. "But I think it's pretty clear in the minds of all here that maintaining the best record would be key."

Farrell said he'll also rest key members of the bullpen who have been used frequently throughout the season. Farrell wouldn't say who, but Koji Uehara (71 1/3 innings), Craig Breslow (56 2/3 innings) and Junichi Tazawa (67 innings) are prime candidates to receive consecutive off-days.

"This is where Ryan Dempster going to the bullpen will help out in that regard," Farrell said.

John Lackey will head to the bullpen for Tuesday's game against the Rockies and should pitch one inning of relief to stay fresh before one final regular-season start against the Orioles.

Boston will also monitor pitch counts on its starters. Jon Lester, who threw 123 pitches in his seven innings on Friday, shouldn't be reaching a pitch count close to that number in his final start.

"Unlikely," Farrell said. "He's going to have plenty of rest."

Jason Mastrodonato is a reporter for MLB.com. Follow him on Twitter @jmastrodonato. This story was not subject to the approval of Major League Baseball or its clubs.