MINNEAPOLIS -- Before injuries sidelined Matt Tolbert and Nick Punto last month, the Twins had plans to start using Brendan Harris more at third base rather than in the middle of the infield.

Those plans haven't been completely erased, manager Ron Gardenhire indicated on Thursday.

Mike Lamb got a surprising start at third base for Thursday's series finale, with the Twins facing Orioles left-hander Garrett Olson. Lamb has struggled against southpaws this season, batting just .091 (2-for-22). He has often sat when the Twins have faced a left-handed starter.

But with infielder Matt Macri having been optioned back down to Triple-A Rochester on Wednesday night to make room on the roster for starter Scott Baker, Gardenhire said that his best option was to stick with Lamb at third on Thursday.

However, that could change with a little more work at the position for Harris.

"I left Lamber in there, because I just haven't seen Harris enough at third base to know whether he is really comfortable there yet," Gardenhire said. "But I'm going to get him more and more ground balls over there."

Harris would give the Twins a right-handed-hitting option to use at third when they face left-handed pitching.

That wasn't such a concern on Thursday as Olson hasn't been particularly tough this year on lefties, who are batting .302 against the southpaw.

And it's Gardenhire's hope, with Lamb starting to look more comfortable at the plate, that the third baseman will begin to hit lefties, too. Prior to this season, Lamb was a career .268 hitter vs. left-handers.

"This year, he's struggled early against lefties," Gardenhire said. "Maybe since he started swinging the bat a little better now, it will be a little easier for him to hit some lefties. That would be nice to see if he can."

Lamb was one of the few lefties that Gardenhire didn't rest on Thursday. First baseman Justin Morneau also was in the lineup, making his 60th straight start this year, but Craig Monroe got the nod at designated hitter in place of Jason Kubel and catcher Joe Mauer was given the day off as well, with Mike Redmond making the start behind the plate.

Mauer has been one of the Twins' hottest hitters, batting .364 with two home runs and 10 RBIs over his past 15 games. And Gardenhire acknowledged that resting Mauer is never easy.

"But you've got to," Gardenhire said. "That's why he's swinging good ... because we are able to give him a few breaks here. If you beat him up, he won't have any legs underneath him to hit."