To make room for Holland, the Rangers have designated right-hander Josh Rupe for assignment. The left-handed Holland, who will be making his major league debut, had one start for Triple-A Oklahoma after nearly earning a spot in the Rangers bullpen out of spring training. Holland allowed four runs in four innings while taking the loss in his lone start for Oklahoma.

He will work out of the bullpen for Texas.

The Rangers view the 22-year-old Holland as a future starter, but the current need is in the bullpen, where Texas relievers posted an AL-worst 8.63 ERA in the first 10 games.

"We felt Derek was the best option for our pen," Rangers general manager Jon Daniels said. "We talked in spring training about breaking camp in this role. We feel he's a strike-thrower who has the makeup to handle (big-league pressure)."

Holland was scheduled to start for Oklahoma on Saturday night before getting the call from Daniels earlier in the day. At first, Holland thought someone was playing a prank. Once he realized Daniels wasn't kidding, he packed and made the 3-hour drive from Oklahoma City to Arlington.

"I didn't even believe it," he said. "I thought it was a joke. It hasn't sunk in and probably won't until I get out there."

A 25th round draft choice in 2006, Holland was 2-0 with a 3.97 ERA in five relief outings for Texas in spring training. Holland was the Rangers' 2008 Nolan Ryan Minor League Pitcher of the Year, going 13-1 with a 2.27 ERA in 26 starters at three different levels with 157 strikeouts and 40 walks.

"We're trying to straighten this bullpen out as best we can," Rangers manager Ron Washington said. "He's not here just to hold a spot. (Bringing up Holland) was earlier than expected because he's had only one start. But he has an idea of what he's doing. He pounds the strike zone, he isn't afraid, he makes adjustments. We'll see how it goes. He's our future and he's here."

Texas has 10 days to trade, release or outright Rupe to the minors. He posted a 15.43 ERA in four relief outings this season, allowing multiple runs in three straight appearances.