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8/24/2014 8:06 P.M. ET

Daniels: Holland to make rehab start Thursday

ARLINGTON -- Derek Holland simply reached down to pick something off the ground in the dugout during Friday's game before feeling a sharp twinge in his back.

A team trainer took him behind the dugout but couldn't put much pressure on Holland's back without him being in serious pain. He couldn't sit down or turn around, much less pitch.

"I didn't realize how fragile I am," Holland said. "A freak thing, as always… I was just like, 'You've got to be kidding. Is this seriously happening?'"

The back spasms kept the Rangers' left-hander from making his sixth rehab start in Las Vegas for Triple-A Round Rock on Sunday, although general manager Jon Daniels said he'll make it Thursday -- the last day of his 30-day rehab assignment.

"He'll go out and play catch tomorrow, do some flat-ground work on Tuesday and, if all goes well, he'll start Thursday for Round Rock," Daniels said.

Holland says his back pain is a thing of the past and that he is ready to pitch. He has missed all of this season while recovering from left knee surgery, but is itching to take the mound as a big leaguer again.

"There's no doubt I'm ready. That's for sure. It's just now, are they ready for me to come back?" Holland said. "I'll take whatever they give me. I'm happy to be playing after what I've been through."

"Derek's been saying he's been ready to go since we've had him out there," said Rangers manager Ron Washington. "Now we've just got to wait and see how he recovers from the back spasms and go from there."

Choo under weather; Robertson bats leadoff

ARLINGTON -- Rangers outfielder Shin-Soo Choo was feeling under the weather and left out of the lineup Sunday.

Daniel Robertson replaced Choo in the leadoff spot against the Royals and had a double and scored in the first inning on Adrian Beltre's RBI double.

Choo missed five games from April 22-27 with a sprained left ankle, but has played in each of the 103 games since. Not fully recovered from the ankle injury, Choo has started 23 games at designated hitter this season, but been a mainstay in the Texas lineup. Sunday would have marked his 100th straight start.

"Choo was a little bit under the weather this morning, so I wasn't going to push him," Rangers manager Ron Washignton said. "We're going to take this a day at a time. He'll let us know. But today we just weren't going to push it."

Washington did not know if Choo would be available off the bench Sunday, or if he would be ready to come back to the lineup for Monday's series opener in Seattle against the Mariners. Choo hit his 14th career leadoff homer Saturday, and is batting .242 with 13 home runs and 40 RBIs this season.

Andrus seeing ball better

ARLINGTON -- Elvis Andrus started this season in a slump, his batting average plummeting to .217 at one point in early May.

But the Rangers shortstop has hit .287 in the 98 games since, and was up to .271 on the season entering Sunday. Andrus is hitting .289 in August, and is close to doing something this month that he hasn't done all year -- walk more than times than he strikes out.

"I usually always get more walks in the second half than the first half," Andrus said. "Early in the year, I think everybody's figuring out how to throw you so I'm a little more aggressive. Usually in the second half, I know what their plan is going to be against me so I have a better idea on how to have better at-bats."

Andrus has walked 10 times this month, one shy of a season-high, and struck out 11 times. In his career, he has walked 8.1 percent and struck out 13 percent of his second-half plate appearances while walking 7.9 and striking out 13.5 percent of his first-half plate appearances. Andrus is also a better second-half hitter than in the first half, batting .280 after the All-Star break and .269 before it over his career.

"Early in the year, I was actually hitting a lot of ground balls to third and shortstop," Andrus said. "When I do that, I know my approach is not in the right place. Right now, I'm hitting the ball more middle and away and that means I'm seeing the ball, letting it travel a little longer."

Worth noting

• Before accomplishing the feat Saturday, the last time Shin-Soo Choo homered on the first pitch of a game was on June 29, 2013, off Nick Tepesch, the Rangers starter in Saturday's loss.

• Choo's homer to lead off Saturday's game was the only one the Rangers hit that night. The Rangers have now lost 12 straight games when hitting only one home run.

• Jim Adduci snapped a 0-for-26 slump with a single to left in the fifth inning Saturday. He is batting .174 in 39 games this season.

• Scott Baker became the ninth Rangers pitcher to start five games Sunday. Only the Yankees, with 10 pitchers making at least five starts this year, have more.

Christian Corona is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.