GLENDALE, Ariz. -- The D-backs trimmed their roster by sending eight players to Minor League camp on Friday, including highly touted pitching prospect Trevor Bauer.

Bauer was optioned to Double-A Mobile, while pitchers Sam Demel and Barry Enright and outfielder David Winfree were optioned to Triple-A Reno. Pitcher Chris Jakubauskas and infielder Rusty Ryal were reassigned to Reno, and pitcher Charles Brewer and third baseman Matt Davidson were assigned to Mobile.

Most of the attention, though, was focused on the decision to send down Bauer, the third-overall pick in last year's Draft.

The right-hander compiled a 3.60 ERA in four games, three of them starts.

"He had a great spring for us," D-backs manager Kirk Gibson said. "We really enjoyed our time with him as well."

It is typical for teams to send down starting pitchers at this time of the spring because members of the rotation begin to pitch deeper into games and there are fewer innings to go around.

Bauer, in particular, likes to throw a lot, and in order to get his pitch count up so he's ready to start the Minor League season, he has to throw longer than the three innings he did in his last start on Tuesday.

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Bauer's pregame routine is unique in that he plays long toss from foul pole to foul pole and he throws more in between starts than most. The D-backs have been flexible with him. The only concession they asked him to make was to not wear headphones on the field while doing his pregame warmups.

In his last start, Bauer's long toss took longer than usual, and he had to rush his warmup pitches.

"He's very unique," Gibson said. "He's got great velocity, he's got great endurance. We'll continue to try to keep him within his comfort zone. At the same time, he was late the other day, he's got to clean that type of stuff up."

This will be Bauer's first full professional season, so whether his intense throwing program can withstand the rigors of starting every fifth day instead of once per week, as he did at UCLA, remains to be seen.

"He has a different type of capacity than most to do more," Gibson said. "Will he continue to hold up? We hope so. Nobody really knows. I mean he throws a lot. And far."

While Bauer and Brewer were sent out, the D-backs kept fellow top pitching prospects Tyler Skaggs and Patrick Corbin.

"I'm not going to go into all the reasons we decided to do it that way," Gibson said. "We knew we had to send two of the young kids down, and we made the decision that those were the guys that would go down. Don't read too much into it, I guess, is what I'm saying."

With the rotation set and the bullpen looking all but locked in, Gibson said he expected Skaggs and Corbin to start the year in the Minors, but both have made good impressions.

"I'm not saying they won't be here, but in all likelihood they'll probably go back [to the Minors]," Gibson said. "If we could do it, we'd probably want them to go to the Minor Leagues, pitch and get established and be ready if we need something down the road. That doesn't mean I can't change my mind."