Manager Ron "Wash" Washington.
The Texas Rangers have lost the leading candidate to be their No. 5 starter for at least a month.
Left-hander Martin Perez broke his left forearm Sunday when he was hit by a line drive in a 7-6 loss to the Seattle Mariners, and he will be out into April.
Perez was struck on the arm just above the wrist by a liner off the bat of Brad Miller. The top prospect dropped to the ground as the ball deflected off his arm toward second base for an infield single.
"I don't really know where the ball ended up," Washington said. "He was on the ground and I went out to him. We'll just have to see what happens."
X-rays revealed Perez had broken his ulna bone and the Rangers said he will not throw for about four weeks. It will then take several weeks of rehabilitation before he could pitch in the major leagues.
Texas said Perez will continue his cardiovascular and conditioning program while his arm heals.
Perez, the No. 17 prospect on Baseball America's top 100 list in 2010, made his big league debut last season. He was 1-4 with a 5.45 ERA in 12 games last year, six starts.
On Sunday, he pitched a scoreless fifth inning in relief then walked his first two batters in the sixth before getting hit. In his first spring training start, he retired all six batters he faced, with two strikeouts.
Perez was expected to earn the fifth starter spot out of camp while Colby Lewis recovers from July 27 elbow surgery. But Lewis is ahead of schedule and could be back by the end of May.
For Seattle, Jesus Montero doubled, homered, drove in two runs and scored twice runs and Kendrys Morales hit his first home run of the spring for Seattle, which won its ninth straight.
Home run power has been noticeably absent in the Pacific Northwest since the Mariners moved to Safeco Field from the hitter-friendly Kingdome. Seattle has finished no better than 10th in the AL in home runs since 2002 and last year the Mariners finished with 149, 11th best in the league.
This spring, however, Seattle leads the majors with 22 home runs in 10 games. The Mariners have at least one homer in every game and have had multiple homers in seven straight.
"Just from batting practice, these hitters have a lot of power, a lot of confidence," said Mariners starter Joe Saunders. "I hope they can carry it into the regular season."
Saunders, who signed a one-year, $6.5-million contract with Seattle last month, bounced back from a rough first outing to throw two scoreless innings, allowing one hit and one walk.
"I don't put much into spring training results," said Saunders, who gave up two runs on three hits in his single prior inning February 26 against Milwaukee. "I learned a long time ago it's about staying healthy in spring training. As long as my arm feels good and I'm healthy, that's what I'm looking for."
Rangers closer Joe Nathan made his first appearance of the spring in the fourth inning, allowing one hit and walking one in his lone inning.
The 38-year-old right-hander has been healthy but, given the six-week spring training schedule, Washington elected to take things slow and keep Nathan working primarily in bullpen sessions.
"I don't know where I am with arm strength," said Nathan, who had 37 saves in 66 appearances in 2012. "If it's different, I can't tell. These games are just preparation to get ready for opening day. Regardless of who's standing in the box you want to go out there and get yourself ready."
Rangers prospect Justin Grimm allowed six runs on six hits and two walks with four strikeouts in 2 1-3 innings.
"He got the ball up," Washington said. "You get the ball up to those big boys, they're going to hit it out."
NOTES: Saunders threw 16 of 29 pitches for strikes. . Rangers RF Engel Beltre returned to the lineup for the first time since straining his left rhomboid in the spring opener February 22 against the Royals and was 1 for 3 with a triple. Beltre will play again Monday before the team decides whether to clear him to participate in the World Baseball Classic. . OF Michael Saunders and 3B Alex Liddi made their last start for the Mariners ahead of the WBC. Saunders will represent Canada while Liddi plays for Italy. LHP Oliver Perez also is leaving camp to play for Mexico. ... Mariners RHP Jon Garland, who missed 2012 after labrum and rotator cuff surgery in July 2011, makes his second start of the spring against Colorado. . RHP Yu Darvish, coming off throwing two perfect innings in his spring debut, takes the mound for Texas against San Diego.