MINNEAPOLIS -- The Twins swapped left-handers in their bullpen on Thursday, calling up Brian Duensing from Triple-A Rochester and sending down Sean Henn.

Duensing, 26, will join the team for the start of its three-game series with the Tigers on Friday night. To make room for Duensing on the roster, the Twins have optioned Henn back to Rochester.

Duensing was on the Twins' Opening Day roster, but he made only one appearance -- allowing two runs on two hits over three innings in Chicago -- before being sent back to Rochester on April 13, when Scott Baker was activated from the disabled list.

In 13 starts for Rochester, Duensing went 4-6 with a 4.66 ERA. He'll be back in the bullpen like he was during his first stint with the Twins earlier this year, and the club could try to use Duensing as a left-handed specialist.

"We think at this point that Brian Duensing will be able to help us more short-term than Sean Henn," Twins general manager Bill Smith said. "Sean came up and did a good job early on. He's had a little trouble lately, especially against left-handers, and that's one thing we need is somebody that can go left-left."

Henn, who signed with the Twins as a Minor League free agent this winter, posted a 7.15 ERA in 14 appearances for Minnesota since having his contract purchased on May 19. The left-hander had allowed just two runs over his first seven appearances (seven innings), but he has posted a 14.54 ERA over his past seven outings (4 1/3 innings) -- allowing seven runs while also issuing five walks.

"The first few weeks he was here, he threw the ball well and threw it over," Smith said. "He's been a little more tentative of late. We hope he can go down there and regain the control and the confidence he had when he came up."

Smith also confirmed that the club officially released right-hander Luis Ayala on Thursday. Ayala had been designated for assignment on June 22 after having asked for a trade three weeks earlier. The 31-year-old right-hander went 1-2 with a 4.18 ERA in 28 relief appearances for the Twins.