MINNEAPOLIS -- Change has come to the Twins' starting rotation, with the first major shake-up of the season coming on Friday with Matt Shoemaker's move to the bullpen.

Rookie right-hander Bailey Ober assumed Shoemaker's rotation spot on Friday and threw five strong innings, earning another turn in the rotation. Meanwhile, Shoemaker was immediately pressed into action for two innings of relief and gave up two runs in the ninth inning of a 6-4 loss to the Astros in the series opener.

• Injuries and Roster Moves

The Twins discussed a change in the aftermath of Shoemaker's last start in Kansas City on June 4, when he allowed nine runs (eight earned) in one-third of an inning, raising his season ERA to 7.28. The Twins informed Shoemaker of the move on Thursday.

"I know I can be a really good starter again," Shoemaker said. "I've not been recently, and I wish I could fight the team on it and I wish I could fight [manager Rocco Baldelli]. That's what we were laughing about. I said, ‘Listen, I want to fight you right now and say, no, let's not do this.' But, realistically, I've not been doing well."

Shoemaker said there haven't any discussions about returning to the rotation in the near future, especially considering the Twins' glut of starting pitchers on the active roster and the impending return of Kenta Maeda, who will start on Monday in Seattle in his reinstatement from the 10-day injured list.

"In regards to starting, right now, unfortunately, that's not even a thought, because, hey, I'm in the bullpen right now," Shoemaker said. "I've got to do the best I can to be ready and help this team win and get myself going, right? If starting comes up in the future, great. So be it. If it doesn't, so be it. Just take it one day at a time."

The 34-year-old right-hander, who was signed to a one-year deal in the offseason to fill the No. 5 slot in the rotation, has made eight relief appearances among the 123 games he has pitched as a big leaguer over the past nine seasons. His most recent outing out of the bullpen was in 2015.

Shoemaker last pitched regularly in relief in college, when he served as the closer at Eastern Michigan University during his sophomore season.

Shoemaker isn't sure exactly what role he'll fill in the Twins' bullpen, though his assumption is that he'll begin in long relief as he adjusts to having to prepare every day. He has picked the brains of fellow relievers Taylor Rogers and Tyler Duffey, who also converted from starting, to discuss their preparation and mindset.

"I'm used to having whatever time you need to get ready for a start," Shoemaker said. "So kind of incorporating things that I already do into a much shorter time frame, but also doing it in the second inning, in the fourth inning, in the sixth inning, just to get your body ready if you're called on. So like I said, it's definitely different, but I fully embrace it."

Baldelli said he and the staff have had plenty of discussions over the past two days about how they'll line up their starting pitchers. Maeda's start on Monday will come in the spot Randy Dobnak has held in the past four trips through the rotation.

At that point, the Twins will have a decision on their hands as to whether they'll stick with Ober, Griffin Jax or Dobnak, who has struggled considerably in two of his past three starts. Jhoan Duran, ranked by MLB Pipeline as the Twins' No. 5 prospect, is expected to need more time in Triple-A before he'll be a candidate for the Major League roster.

"We had a lot of things to figure out, and we had to kind of mix and match and make it all work -- make it work on the schedule, too -- and line it all up," Baldelli said. "This is kind of the way that we think it works best right now, and it will take a little bit of adjusting. We have a few changes going on, but we think all for the better."

Maeda to return Monday in Seattle
Maeda felt confident that the velocity on his fastball and the customary movement on his offspeed pitches were back during his rehab start for Triple-A St. Paul on Wednesday, and the Twins are confident enough in his recovery that they expect him to make the start Monday against Seattle.

The right-hander was placed on the injured list on May 23 with a right adductor strain -- exhibiting tightness in his groin -- after which he also had to recover from some generalized arm weakness.

Considering Maeda threw only 54 pitches in his rehab start, the Twins expect him to have a lower-than-normal pitch count, but they still hope to get good length out of their Opening Day starter.

"I think he can give us a good, full start," Baldelli said. "We'll let him pitch, and I think the way that the game goes will tell us a lot about what we need to know. How hard he's had to work to get through some of the innings will certainly factor in, and we'll make a call, probably more off of how he looks and how he's doing than on a pure pitch count.