ARLINGTON -- Derek Holland, one of the Rangers' top Minor League pitching prospects, has arrived at the Major League level. The Rangers are counting on it to be for good, even if he is starting out in the bullpen.

Holland was called up from Triple-A Oklahoma City on Saturday to reinforce the Rangers' struggling bullpen. To make room, the Rangers designated reliever Josh Rupe for assignment.

"I don't even know -- it hasn't even hit me yet," Holland said, standing in the Rangers' clubhouse before Saturday's game with the Royals. "It probably won't hit me until I get out on the field. Even on the drive down here [from Oklahoma City], it didn't hit me."

Holland has been used almost exclusively as a starter in the Rangers' farm system since being taken as a draft-and-follow player in the 25th round of the 2006 First-Year Player Draft. But the Rangers have decided to break him in at the Major League level as a reliever.

"As we looked at it, Derek was the best option for our bullpen," general manager Jon Daniels said. "It's something we discussed in Spring Training, breaking camp in this role. We feel he's a strike thrower with the stuff and the maturity to handle it. He'll be used initially in the bullpen.

"Obviously, we see him as a starter down the line, but right now he'll be in the bullpen."

Rangers relievers went into Saturday's game with an 8.63 ERA, having allowed 43 hits and 21 walks in 32 1/3 innings. They had allowed runs in eight of the club's 10 games, and the biggest concern is in middle relief, which is where Holland will be used.

"We're trying to straighten out the bullpen, especially in the middle," manager Ron Washington said. "We looked down there, and he was the best we have. We'll use him as a long guy and probably try to get him multiple innings whenever he comes in. It will probably be before the eighth.

"We'll watch him closely. We certainly won't abuse him. We won't leave him out there to take a beating."

Holland said he was used occasionally as a reliever at Wallace State Community College in Hanceville, Ala., before being drafted by the Rangers.

"I closed a little bit," Holland said. "Relieving is fine with me. When the time comes, you still have to go out and throw. Nothing has changed. I feel good. I feel ready."

A year ago, Holland was pitching at Class A Clinton, but he has flown through the Rangers' system. He was 7-0 with a 2.40 ERA in 17 starts at Clinton, 3-1 with a 3.19 ERA in five starts at Double-A Bakersfield and 3-0 with a 0.69 ERA in four starts at Double-A Frisco. Overall, Holland was 13-1 with a 2.27 ERA last season, striking out 157 and walking 40 in 150 2/3 innings to earn the Nolan Ryan Rangers Pitcher of the Year Award.

Holland made one start at Oklahoma City, allowing four runs in four innings. That was just his fifth start above the Class A level.

"We feel he's ready to handle this thing," Daniels said. "I'm not saying there won't be bumps in the road, but he's here to contribute to the team right now in the bullpen. We'll see where that goes."

Overall, Holland has pitched 221 2/3 innings in the Minor Leagues. By contrast, Kevin Millwood pitched 503 innings in the Minor Leagues before being called up to the Major Leagues for the first time.

But Tim Lincecum, the Giants' No. 1 pick in the 2006 Draft, pitched in just 62 2/3 innings in the Minor Leagues before making his Major League debut on May 6, 2007. Lincecum was the National League Cy Young Award winner last season.

"I think there are plenty of examples of guys coming quickly," Daniels said. "Derek's had 220 pro innings, and that's obviously on the low end. But other guys have had similar numbers and gone to the big leagues and had success. We feel his makeup and aptitude and stuff will lend him to having success."

Right-hander Neftali Feliz is another of the Rangers' top pitching prospects who will get strong consideration for promotion to the big leagues. He is 2-0 with a 2.00 ERA in two starts but has also walked eight batters in nine innings. A promotion to the Rangers' bullpen could be in his near future.

"Possibly," Daniels said. "Possibly. Everybody is considered individually. But this is about Derek. We'll continue to evaluate candidates as we go along. We felt Derek was the best of our options and a pretty good one."

Holland was 2-0 with a 3.97 ERA in five Cactus League relief appearances, and he was with the Rangers right up until the club broke camp. The Rangers insisted in Arizona that Holland was not going to make the team, but Daniels said it was discussed.

"We were committed not to do it," Daniels said. "But there was sentiment that the best team would have included Derek."

By waiting this long, the Rangers delayed the possibility of Holland becoming a free agent until after the 2015 season rather than 2014. Daniels said that was not a major consideration.

This is already the second bullpen move made by the Rangers in 10 games this season. Earlier this week, they optioned right-hander Warner Madrigal to Oklahoma City and activated righty Willie Eyre from the disabled list.

Holland was supposed to start for Oklahoma City on Saturday but was replaced by Thomas Diamond.