SCOTTSDALE, Ariz. -- The Indians believe Trevor Bauer is an integral piece to their long-term blueprint. The young pitching prospect just has some development remaining before beginning his career in Cleveland.

On Thursday, the Indians optioned Bauer, along with right-hander Corey Kluber, to Triple-A Columbus, whittling the race for the fifth spot in the rotation down to lefty Scott Kazmir and righty Carlos Carrasco. After spending his first spring with the Tribe, Bauer was looking forward to rejoining the big league club in the future.

"The team is great. It's a great group of guys assembled," Bauer said. "They're a lot of fun. It'll be a fun team, so hopefully at some point I can get up here and enjoy it."

Cleveland also optioned left-hander Scott Barnes to Columbus and reassigned lefty Giovanni Soto to Minor League camp on Thursday.

Over the offseason, Cleveland landed the 22-year-old Bauer from the D-backs as part of a complicated nine-player, three-trade trade in December. Acquiring Bauer was key for completing the blockbuster swap, which was also highlighted by Shin-Soo Choo going to the Reds and Drew Stubbs coming to the Indians.

Cracking Cleveland's Opening Day rotation was going to be an uphill battle for Bauer, as it was, but the right-hander may have complicated matters by attempting to overhaul his mechanics this spring. The pitcher understood the risk involved with that approach, but he tried to focus on the bigger picture, rather than the rotation race in front of him.

"I don't think about making a big league club or not," Bauer said. "I think about my improvement and getting better. If I can improve every day, then that's all I can handle. I made a decision to make some changes that are going to help me long term. That's what I'm doing."

After pitching through a nagging groin issue for most of last season, Bauer implemented changes to his lower-half mechanics in an effort to reduce some strain on his legs. The pitcher said he also adjusted his upper-half mechanics with the goal of becoming more consistent with his strike-throwing ability.

In five Cactus League appearances this spring, Bauer posted a 4.50 ERA with nine strikeouts and four walks in 14 innings of work for the Indians. Against the Angels on Wednesday, he allowed four runs (three earned) in three innings, and was forced from the game after laboring through a 33-pitch third.

After the outing, Bauer said he had been trying to "overwrite 10 years of neuromuscular programming in four or five weeks," which is tough to do while also attempting to make a big league roster.

"I think last year he felt like he didn't pitch completely healthy, and even into the winter," Indians manager Terry Francona said. "So I think he's trying to find a way, I think the word he used is replicate, his mechanics. ... That's the whole idea, because he didn't command his fastball at all [Wednesday]. We tried to press upon him the importance of working ahead and locating his fastball. He completely understands that."

Last season, Bauer went 12-2 with a 2.42 ERA in 22 starts between Double-A and Triple-A in Arizona's farm system. He also endured a rocky four-start (6.06 ERA) stay in the big leagues, where his unique personality rubbed some members of the D-backs the wrong way.

Asked if he feels like fans and media pay more attention to him than other pitchers, Bauer shrugged.

"I don't know what everyone else gets," Bauer said. "That's the fish bowl I swim in. That's all I know. I don't know any different. It's what I'm used to."

Bauer said the Indians organization has been completely on board with the changes he is trying to make.

In the meantime, Cleveland will pick either Kazmir or Carrasco for its lone rotation vacancy.

Kazmir -- in camp as a non-roster invitee -- has not logged a full season in the Majors since 2010, but is attempting a comeback with Cleveland. Through 16 spring innings, which includes three Cactus League appearances and a pair of Minor League starts, Kazmir has allowed four runs (all in a Minor League game on Sunday) on 16 hits with 18 strikeouts and three walks.

Carrasco, who missed all of last season while recovering from Tommy John surgery on his right elbow, allowed four runs on eight hits in five innings against the D-backs on Thursday at Salt River Fields. The right-hander -- a member of Cleveland's Opening Day rotation in 2011 -- finished with no walks and three strikeouts in his fifth Cactus League outing of the spring.

Some poor defense in the third inning contributed to a three-run frame for Arizona.

For the spring, Carrasco has given up 13 runs (12 earned) on 22 hits with 13 strikeouts and four walks in 19 innings of Cactus League play. In his most recent outings, the 26-year-old right-hander has appeared to be more aggressive, compared to his first few appearances of the spring.

"It's been good to see," Indians general manager Chris Antonetti said earlier this week. "It's been very encouraging."

Francona downplayed the importance of any singular performance by Carrasco or Kazmir over the remainder of camp.

"I don't know that it's like a pitch off," Francona said. "I think we'll make our best decision on what's best for our ballclub, when it's time."