BOSTON -- With All-Star second baseman José Altuve already on the injured list with a strained left hamstring, the Astros breathed a sigh of relief on Saturday when Aledmys Díaz -- Altuve’s fill-in -- was diagnosed with a mild hamstring strain and told he won’t have to join Altuve on the shelf.

Diaz, who felt discomfort in his left hamstring while beating out an infield single in the second inning of Friday’s win over Boston and was removed from the game, said he had a grade one strain. Manager AJ Hinch said Diaz likely won’t play on Saturday or Sunday but could return to action as early as Monday’s series opener in Houston against the White Sox.

“I feel better,” Diaz said. “We’re going to take it day by day, and hopefully in a couple of days, I feel 100 percent. We’re in a very good spot right now.”

Diaz did some exercises in the gym early Saturday to strengthen the hamstring and hopes to be able to run on the field on Sunday. He started the first six games after Altuve went on the IL and hit .421 with three homers and 10 RBIs.

“Luckily, the diagnosis is very mild and he’ll be day to day,” Hinch said.

As for Altuve, he ran sprints on the field at Fenway Park prior to Saturday’s game in his first baseball-related activities since suffering a strained left hamstring on May 10 against the Rangers. He was placed on the IL the following day and is eligible to return on Tuesday, but he will need more time.

Still, he was encouraged by the way his leg responded when he got back onto the field and tested it for the first time. He’s very optimistic and said he feels good.

"I’m kind of following [the training staff’s] schedule,” he said. “They always make the right decision, the right move. I’m trusting them and following whatever they got for me.”

Altuve, who was in an 11-for-68 slump in his 20 games prior to going on the IL, is thrilled by how well the team has been playing in his absence. In the six games following his injury, the Astros went 6-0 (entering Saturday) and were hitting .314 as a team, with 15 homers.

“They’re playing really good,” he said. “It’s real impressive what they’re doing right now. Everybody is going out there and swinging the bat really well, and that made me feel way better. It’s not easy to be on the [IL] when your team is losing, and they’re making it way easier for me.”

It’s unclear as to whether Altuve will need a Minor League rehab assignment before being activated.

Playing it safe with Chirinos

On Friday, for the second time in a week, catcher Robinson Chirinos absorbed a foul tip off his mask and was briefly dazed. He wasn’t in the lineup on Saturday, but that had nothing to do with his health, Hinch said. Max Stassi had always been scheduled to start behind the plate.

But the Astros don’t take chances with Chirinos, who missed the entire 2012 season after he sustained a concussion in Spring Training on a foul tip that struck his mask.

“We know the history. ... We want to make sure we err on the side of caution all at times with that stuff,” said Hinch, himself a former catcher. “That’s pretty significant stuff when you’re talking about head injuries and concussions and stuff like that.”

Hinch said that Chirinos gets hit more than any catcher he’s been around.

“I think it’s more unlucky than anything," he said. "He’s handling it fine. It’s predetermined that he was going to sit [Saturday] and catch [Sunday]. When a guy gets beat up, I’m very empathetic with that position and all that he goes through. He seems to get hit by a pitch, he gets hit by a few foul tips a game. It’s the nature of the job. “