"It's hard to be out there and you can't complete any games," Cruz said. "Sometimes you want to run, you want to steal some bases or make some plays, and you aren't allowed to do it 100 percent."
The Rangers later optioned struggling catcher Taylor Teagarden (.037 batting average, 1 for 27 with 17 strikeouts in 10 games) to Triple-A Oklahoma City and recalled catcher Max Ramirez. Jarrod Saltalamacchia (upper back stiffness), the starting catcher on opening day, was activated from the 15-day DL and optioned to Oklahoma City, where he had already played six games on a rehab assignment.
"We've struggled at that position in the early going here, and want to give Taylor an opportunity to go down and get himself right," general manager Jon Daniels said. "We explained to Jarrod, now that he's healthy, we just want to see him go down there and play, get consistent reps, consistent at-bats."
Vladimir Guerrero started in right field against the Chicago White Sox on Tuesday night, and Ryan Garko was the designated hitter. The Rangers called up Craig Gentry to take Cruz's place on the roster.
Cruz first felt a twinge in the hamstring while the team was in Boston, and he had to leave the game in the late innings. On Monday, Cruz left the game after running the bases on a wild pitch in the sixth inning.
"Yesterday I felt great. Even when I went from first to second, I was normal," Cruz said. "When I took off to home plate and made that quick move, that's when I felt it. It was worse than what I did before."
An MRI confirmed the hamstring strain, the team said. Cruz said an X-ray Tuesday showed fluid in the affected area. He isn't eligible to return to the lineup until a mid-May series at home against Oakland.
Manager Ron Washington said Cruz had "only a first-degree strain" but was very sore. Washington said the slugger was going to have to miss at least five to seven games and the DL move was made because the Rangers couldn't afford to be short on the bench that long.
Cruz, an All-Star who hit 33 home runs in his full major league season last year, is batting .323 with a team-high seven homers and 17 RBIs. He also leads the American League with a .758 slugging percentage and is second in home runs behind Paul Konerko. Cruz also leads the Rangers with 47 total bases and 12 extra base hits.
"He's one of our best run producers," Washington said. "We'll do the best we can to supplement his loss."
David Murphy, a left-handed hitter, wasn't in the lineup Tuesday night but Washington said he would get most of the time in right field against right-handers. Murphy had a two-run double and a run-saving catch Monday night after replacing Cruz.
Guerrero signed with the Rangers after the Los Angeles Angels showed little interest in retaining the eight-time All-Star and former American League MVP after he had two stints on the disabled list last season for a torn right pectoral muscle and strained left knee.
Through his first 18 games with Texas, Guerrero hit .371 with two homers, 13 RBIs and three stolen bases.
"I feel good. I feel great," Guerrero said in the clubhouse before Tuesday's game. "I've been feeling fine since the beginning of spring training."
Washington said he put Guerrero in the outfield with the stipulations of no diving catches and to just get the ball to the cutoff man if it got past him. Then the manager indicated he was partially joking.
"The one thing I badly don't want to do is hurt Vlad," Washington said. "Now I can't control his reactions. It's just a running joke. He's a pro."
Washington said the loss of Cruz wouldn't accelerate the return of second baseman Ian Kinsler, who Tuesday was set to play the second of three rehabilitation games at Double-A Frisco. Kinsler has been on the disabled list since spraining his right ankle during spring training.
"We have a plan with Kinsler, we want to finish the process," Washington said. "We're not going to push him. He has two more days to play. He is going to play two more days."
If there are no setbacks, Kinsler will be activated before Friday night's game in Seattle.
Gentry, 26, is hitting .293 (17-for-58) with two homers and 12 RBIs in 17 games for Triple-A Oklahoma City this season. He has 11 strikeouts and eight walks and is 5-for-6 on stolen base attempts.
Gentry made his major league debut as a September callup last season. He was 2-for-17 with a double and an RBI in 11 games (five of them starts). He was taken by Texas in the 10th round of the 2006 draft.