FORT MYERS, FLA. – ByungHo Park, the most impressive player in Twins spring training, will start the season in the minor leagues.

In a surprise move, the Twins revealed Thursday they will keep 13 pitchers on the roster and Park will begin his season at Class AAA Rochester.

Park has a .353 average with a team-leading six home runs and 13 RBI in exhibition games.

Twins players were shocked as news of Park's departure swept the clubhouse Thursday. Park, after initially looking stunned upon leaving manager Paul Molitor's office, was confident as he spoke to reporters.

"It's bitter news, but I'm not disappointed," Park said through an interpreter. "I know what I do here. My mind-set when I started this spring training camp, I know what I can do. My goal is the same. I know I can do it, wherever I start."

Molitor walked over to Park's stall to offer more words of encouragement.

"He encouraged me to keep doing what I have been doing here at spring training camp and he trusts me that I can do it," Park said. "It was a good pep talk."

Twins Chief Baseball Officer Derek Falvey said the team began considering switching to a 13-man staff in recent days as concerns about pitchers were raised. Adalberto Mejia, who won the fifth spot in the rotation, is a rookie. Starter Hector Santiago might not be ready to pitch deep into games since he missed two weeks to participate in the World Baseball Classic. And Phil Hughes, who is coming off thoracic outlet surgery, might not be ready for long outings, either.

The Twins decided that having an extra arm available would be prudent.

"We felt there could be some benefit to having the additional guy in the bullpen," Falvey said. "It wasn't that Park was necessarily beat out at his position, it was that we decided to go with a different roster configuration. Our message to ByungHo was that he continue to progress down the path he's going down. We're confident we're going to need more than 25 during the course of the season."

Dominoes fall

The Park decision sends a ripple through the 25-man roster:

• Robbie Grossman will likely be in the Opening Day lineup at designated hitter against Kansas City on Monday with Park demoted and Kennys Vargas battling a foot injury. Grossman is a switch hitter who would bat righthanded against the Royals' lefthanded Danny Duffy.

• Chris Gimenez, officially named the backup catcher, will play first base when Joe Mauer needs time off. Miguel Sano could be designated hitter in a few games, with Eduardo Escobar playing third base.

• And Tyler Duffey makes the team as a reliever after losing the fifth-starter competition to Mejia.

In addition to covering for the pitching staff, the Twins would have had to make room on the 40-man roster for Park, who was taken off the roster in early February when reliever Matt Belisle signed. Falvey downplayed that factor, saying that 40-man roster considerations are ongoing. The Twins had to make room for Craig Breslow and Gimenez during camp and might not want to add a third player.

Molitor looked disappointed as he talked about having to tell Park he was cut.

"It was really hard," Molitor said. "There's no denying he has done what we have asked him to in this camp. He put himself in a good place, how he worked, the condition he came in. He swung the bat, the consistency in his at-bats, the calmness in the box. He's shown the power that his track record indicates he has.

"You guys can do your due diligence on trying to understand some of the complications surrounding the things that made it more challenging to find a way to get him here."

Roster set

On Thursday morning, the Twins optioned catcher John Ryan Murphy to Class AAA Rochester and reassigned catcher Eddy Rodriguez, infielders Benji Gonzalez, Matt Hague, Ben Paulsen and Park and outfielder J.B. Shuck to minor league camp.

Infielder Ehire Adrianza (right oblique strain) and lefthanded pitcher Ryan O'Rourke (left forearm strain) went on the 10-day disabled list.

Mejia will be joined in the starting rotation by Ervin Santana, Hughes, Kyle Gibson and Santiago.

Twins Opening Day starters are set with Mauer at first, Brian Dozier at second, Jorge Polanco at shortstop, Sano at third, Jason Castro catching and an outfield of Eddie Rosario, Byron Buxton and Max Kepler. Gimenez, Escobar and versatile Danny Santana will be the reserves.

Rule 5 pick Justin Haley and Michael Tonkin on Wednesday became the final two relievers to make the team. Also in the bullpen are closer Brandon Kintzler, Duffey, Breslow, Ryan Pressly, Belisle and Taylor Rogers.

Players were told about the moves before the team got on the bus to Port Charlotte to play the Rays, the Twins' final preseason game against a major league team. The Twins will play their Rochester farm team Friday before heading to the Twin Cities for a Sunday workout.

The Twins called up seven players last April, including five pitchers. Falvey said that major league teams on average used 17 pitchers by May 15 last year — hence the insistence on looking at the big picture over the event that is Opening Day.

As the games begin and pitchers establish themselves, the Twins could go back to 12 pitchers.

"Short term," Molitor said. "Short term."