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Caleb Thielbar walked off the mound Wednesday without recording an out against the four Colorado Rockies batters he faced.

It was the latest rough outing this season for the 37-year-old lefthanded reliever. He has yielded an 8.04 ERA through 23 appearances, permitting 24 hits and 14 earned runs in 15⅔ innings with nine walks.

"He's figured things out in his career many times, and he's had to adjust many times," Twins manager Rocco Baldelli said. "In some ways, he knows what he's aiming at."

Two of the three runs Thielbar allowed in the Twins' 17-9 win were unearned after Carlos Correa committed an error on a slow ground ball. But he walked two hitters and surrendered a double to catcher Jacob Stallings on a slider in a two-strike count.

Thielbar, a Randolph, Minn., native, started the season on the injured list because of a left hamstring strain. Since he returned, he has never fully looked like he did last year when he was used as a setup man in postseason games. He has been crushed by righthanded hitters (.457 batting average, three homers), and his strikeout rate has dipped.

"He's a guy that's had exceptional command of his four-seam fastball and his big breaking ball that has been such an effective pitch for him," Baldelli said. "Part of what also makes it good is those are very consistent pitches for him. He has very good feel for them.

"In the outings that haven't gone his way … the command of those pitches wasn't where they needed to be."

Thielbar attempted to lean on his off-speed pitches Wednesday, but three of his first four sliders were outside the strike zone and five of his six curveballs were balls.

"He's a very smart guy, cerebral when it comes to his craft," Baldelli said. "He's going to work."

Jay Jackson returns

The Twins added Jay Jackson to their bullpen Wednesday, and he allowed two hits and a run in the ninth inning while striking out three.

Jackson replaced Louie Varland on the 26-man roster after Varland made a spot start Tuesday, and Diego Castillo was designated for assignment.

"He's capable, and he's a good option to bring back in this role right now," Baldelli said of Jackson. "Lou did his job very well. We're not capable of carrying six starters."

Jackson, 36, was designated for assignment May 19 and pitched in three Class AAA games. He admits there was surprise when he was initially designated for assignment, but he knew his 6.85 ERA put him at the bottom of the bullpen depth chart.

"You have to go through different obstacles when you get older, and you have to figure different things out each year," Jackson said. "This has just been one of those challenging years where I had a crazy offseason where I didn't get as right as I wanted because I was at the hospital every day with my son [born nearly four months premature]. I wasn't preparing as well as I probably should have, but this game, still, I have to go out there and perform with what I have."

Etc.

* Brock Stewart threw five pitches off a mound Wednesday, his first time pitching off a mound since he went on the 15-day injured list May 3 with right shoulder tendinitis.

* Injured Twins reliever Justin Topa, sidelined all year with a tear in his left patellar tendon, has played catch for the past week. He's hopeful he will be cleared to begin pitching off the mound after an upcoming follow-up medical visit in Cincinnati.

* Matt Wallner hit a two-run triple and Tony Kemp produced three hits as the St. Paul Saints rolled to a 7-2 road win over the Louisville Bats. Starting pitcher Adam Plutko gave up five hits and one run in 5⅔ innings while striking out five.