Mike Trout sits out against Astros because of hamstring tightness

That Mike Trout minor hamstring tightness that caused the Angels to rest him Thursday is hinting at becoming a more lingering problem.

The two-time American League MVP was a late scratch Saturday when his left hamstring again tightened during pregame warmups.

After sitting out Thursday’s series finale in Seattle because of the hamstring issue, he started Friday in the opener against the Houston Astros and appeared to run without discomfort.

He was scheduled to hit in his normal third spot Saturday. The Angels did not announce he was not playing until just before first pitch.

They said after Trout felt discomfort in the hamstring during warmups, it was decided to scratch him for precautionary reasons and called him day to day.

Richards still in limbo

If the waiting really is the hardest part, Garrett Richards is putting the worst behind him. Trouble is, right now it remains the hardest part.

Richards has been on the disabled list for one month because of nerve irritation in his right biceps, and his return remains very much unknown.

“It’s pretty much the same as it’s always been,” Richards said. “We’re just kind of waiting for it to heal.”

Richards was supposed to be the Angels ace but missed the final 137 games last season after he tore his ulnar collateral ligament. Instead of the more common Tommy John surgery, he had a stem-cell injection.

The ligament appears sound, but one game into this season came the nagging biceps issue.

“It’s frustrating when you go through everything you went through last season and then this happens,” he said.

“But what are you going to do? You can either feel sorry for yourself or keep trying to get better every day, and hopefully everything comes out good on the other side.”

While playing his unwanted waiting game, Richards has yet to pick up a baseball.

Cron to start rehab

C.J. Cron (bruised left foot) joined triple-A Salt Lake City on Saturday and is scheduled to make his first rehab appearance Sunday. He fouled a pitch off the foot April 29.

Manager Mike Scioscia was uncertain how many rehab games Cron would play before rejoining the Angels. He can come off the disabled list Wednesday.

“We’re going to start with the first one and see where it goes,” Scioscia said. “It’s good for him to get some at-bats instead of sitting around.”

Valdez designated

Right-handed reliever Jose Valdez was designated for assignment to allow the Angels to make a trade of minor league relievers.

Valdez, purchased from the Detroit Tigers last season, had appeared in one game this year, giving up a walk and two-run homer to Carlos Gomez in Texas last Saturday.

The Angels picked up right-hander Damien Magnifico, 25, from the Baltimore Orioles in exchange for right-hander Jordan Kipper and assigned Magnifico to Salt Lake City.

Magnifico was 1-0 with a 9.95 ERA for triple-A Norfolk, but last year pitching for the Brewers’ triple-A Colorado Springs team had 18 saves.

sports@latimes.com