ARLINGTON -- Rangers right-handed reliever Chris Martin was optioned to Triple-A Round Rock on Tuesday prior to the club's series opener against the Astros at Globe Life Park.
Martin is 1-1 with a 4.13 ERA in 27 appearances this season. He last pitched Saturday, when he threw a scoreless inning against the White Sox.
The move made room on the 25-man roster for first baseman Ronald Guzman, who returned from the seven-day concussion disabled list on Tuesday, the first day he was eligible to return. Back in the lineup at the No. 8 spot, Guzman went 2-for-4 with a double and two runs scored in the Rangers' 5-3 loss to the Astros.
Rangers manager Jeff Banister said Martin's demotion was to create bench depth. Adrian Beltre, Nomar Mazara and Joey Gallo have each dealt with left hamstring injuries this season.
"Chris hadn't done anything to warrant being optioned," Banister said. "He's got options. Obviously, he's pitched well for us in the bullpen. However, you've got to be able to protect some of the other players on the team, too."
Banister said Guzman passed the concussion protocol three days after he was placed on the disabled list.
"He was a full-go, as far as baseball activities are concerned," Banister said.

The Rangers recalled utility player Ryan Rua from Round Rock last week to replace Guzman. Rua, who is on his fifth tour with the Rangers, was in the lineup and in left field on Tuesday. He went 0-for-4 with an RBI and pair of nice catches.
Rangers beat
• Left-hander Martin Perez will make a rehab start for Round Rock on Thursday against Oklahoma City. It will be the third rehab start for Perez, who threw 73 pitches, allowed two hits and struck out four in six scoreless innings for Double-A Frisco on Saturday.
• Gallo was out of the lineup Tuesday. Gallo, who continues to deal with a left hamstring injury, entered the day hitting just .149 since the start of June. But he did pinch-hit in the eighth inning and drew a walk after a 12-pitch at-bat. He then stayed in the game and played left field.
• The Rangers signed five 2018 Draft picks on Tuesday: shortstop Jax Biggers (eighth-round pick), left-hander Grant Wolfram (18th), right-handers Wyatt Sparks (23rd) and Renton Poole (28th) and third baseman Shea Patterson (39th) . Texas has now signed 32 of its 40 draft picks, including its top 14.