After reliever Justin Topa pitched Friday for Class AAA St. Paul, his third outing on a rehab assignment, the hope was he would join the Twins bullpen this week.

Then came a Sunday setback.

Topa, on the 15-day injured list with left patellar tendinitis, felt more soreness in his knee when he pitched Sunday for the Saints. He pitched a scoreless inning with one hit and one strikeout, but his velocity was down by nearly 3 mph on his sinker.

He threw a bullpen session Wednesday, noting his knee pain comes and goes, but he underwent a magnetic resonance imaging exam this week and he was awaiting the results before the Twins determine his next step.

"Friday was the best it had felt in a very long time, so there was a lot of optimism, especially coming in here Saturday," Topa said. "I played catch with no issues. Everything Sunday morning before the game felt great. The touch and feel felt great. Warming up in the bullpen felt great. Then a couple of pitches in, it kind of flared it up a little bit. It's just frustrating to say the least."

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Topa, a 33-year-old righty, was one of the four players the Twins acquired from Seattle in the Jorge Polanco trade. Anthony DeSclafani, the other major leaguer in the deal, underwent elbow surgery and is out for the season.

Topa dealt with some occasional knee soreness last year when he posted a 2.61 ERA in 75 appearances for the Mariners, but he said the pain was "not to this extent."

"It's very day by day. That's what is frustrating about it," said Topa, who started the season on the IL. "You wake up one day and you think it's on the mend and in a good spot, then you start moving around, you throw and there it is again."

Etc.

* Brock Stewart, sidelined with right shoulder tendinitis, said an MRI showed rotator cuff inflammation, and he remains shut down from throwing. "I've had rotator cuff stuff in the past, so I wasn't shocked when I heard that," he said, adding he hopes he's cleared to play catch as early as this weekend.

* Matt Wallner and DaShawn Keirsey Jr. combined for five hits and five RBI during the Saints' 11-6 road win against the Toledo Mud Hens on Wednesday. Wallner has 10 hits in his last 25 at-bats with three homers and a triple.