HOUSTON – Time is running out on several injured Mariners to return before the end of the season, with just 3 1/2 weeks now remaining on the schedule. But manager Scott Servais said shortstop J.P. Crawford and outfielder Domingo Santana are still pushing to get back, while things are less certain with right fielder Mitch Haniger.

Crawford has been sidelined by a right hamstring injury since Saturday and flew back to Seattle on Sunday to be checked out by Mariners doctor Edward Khalfayan. Servais said the 24-year-old is feeling better and indications are his issue might not be as serious as feared.

“I texted with J.P. last night and he’s feeling really good,” Servais said prior to Thursday’s series opener with the Astros. “The initial look from Dr. Khalfayan was maybe not as severe as they originally thought. He did work out a little yesterday. No baseball activity, but in the weight room, getting after it there. We’ll see when we get back home. But I don’t think it’s going to be as long as the original thought.”

Crawford is one of the Mariners’ core pieces moving forward and has hit .241/.322/.397 with six homers and 40 RBIs in 79 games since being called up from Triple-A Tacoma in May. Dylan Moore is filling in at shortstop in his absence.

“I am hoping to get him back before the end of the year, but I really want him to be 100 percent,” Servais said. “There’s no reason to rush him out there. He really wants to get back on the field, so it’s all good there and moving in the right direction.”

Santana is in a similar situation, as he’s been shut down since Aug. 19 with inflammation in his right elbow. Servais said the big right fielder has begun playing catch without any issues at 60 feet and will gradually increase that with the hope of returning before the end of the month.

Santana was limited to designated-hitter duties for about a month before going on the injured list and Servais didn’t rule out the possibility of him returning to a DH role if he can swing the bat without issue before he’s able to play the outfield.

“I’m curious to see where he’s at when we get home,” Servais said. “I don’t think he’s swung a bat yet. I know he wants to get out there, too, before the season is over. If he feels fine with the bat, I wouldn’t have a problem running him out there at DH. Probably not every day, but certainly against left-handed pitching, it could be helpful for him and for us.”

As for Haniger? That situation remains more uncertain as the 2018 All-Star hasn’t played since rupturing a testicle on a foul ball on June 6. That injury finally healed and he played three Minor League rehab games before being shut down again on Aug. 20, this time due to pain in his lower back.

Servais said Haniger is getting a second opinion in the next day or so on the back and awaiting word on whether there’s any chance he can return this season.

“I don’t know,” Servais said. “I want to stay optimistic and hopefully we can get him back out there.”

Worth noting

• The Mariners have yet to announce a starter for Sunday’s series finale in Houston. Justus Sheffield is lined up to pitch that day against Astros standout Gerrit Cole, but Servais said the rookie right-hander may be held back until Seattle returns home to face the Reds next week as the club looks to monitor his workload in his first full year as a starter.

If that is the case, they likely would go with a bullpen day Sunday, which certainly is workable with 12 relievers on the team now with September callups.

• Second baseman Shed Long hasn’t started yet since being recalled on Tuesday, but Servais said the 24-year-old rookie will get some action soon, including the possibility of time in left field.

After missing seven weeks with a broken finger on his right hand, Long only played four games in Tacoma before getting the callup, so he’s been getting extensive pregame work to get back up to speed.