SEATTLE -- Robbie Ray's return to T-Mobile Park was cut short on Sunday afternoon, as the veteran left-hander was forced to exit with left hamstring tightness in the bottom of the fourth inning of the Giants’ 4-3 loss to the Mariners.

Ray, who was facing the Mariners for the first time since being traded to San Francisco in exchange for Mitch Haniger and Anthony DeSclafani in January, grabbed the back of his left leg after delivering an 0-1 pitch to Justin Turner to lead off the inning.

Head athletic trainer Dave Groeschner and manager Bob Melvin quickly emerged from the dugout to check on Ray, who ended up leaving the game after allowing one run on one hit over three-plus innings.

Ray described the tightness as “minor,” but he’s never dealt with hamstring issues before and felt it was prudent to depart rather than risk making the injury worse. He’s expected to undergo an MRI exam on Monday to determine the severity of the injury.

“I think I just felt it on one pitch,” Ray said. “I felt it kind of tighten up on me. I’ve tried to push through injuries in the past before, and it hasn’t gone well for me. So hopefully, I caught it before anything significant [happened]. We’ll find out.”

Sean Hjelle came on to replace Ray, but he was charged with the loss after giving up three runs on four hits over 2 2/3 innings.

Ray said it’s too early to say whether he’ll be able to avoid a stint on the injured list, but Melvin noted that hamstring injuries tend to require some time to heal.

“Hopefully, he caught it and it’s mild,” Melvin said. “But those things don’t typically take a couple of days.”

Ray missed the first half of the season while rehabbing from Tommy John surgery, and has recorded a 4.70 ERA over his first seven starts of the year. His latest setback could be another big hit for the Giants, who had been counting on their starting rotation to keep them competitive down the stretch.

“I felt like I was getting in a groove, too,” Ray said. “The first inning got a little long on me, but I felt like after that, everything started feeling better. … It’s definitely frustrating, for sure.”

San Francisco’s starters collectively struggled to deliver this weekend, with Hayden Birdsong, Blake Snell and Ray each failing to complete five innings in this series loss to the Mariners. Sunday’s defeat dropped the Giants (66-66) back to .500 and left them five games behind the Braves for the third National League Wild Card spot, further dimming their hopes of making a late playoff push.

The Giants’ pitching depth was thinned after they traded Alex Cobb to the Guardians last month and lost Keaton Winn to season-ending right elbow surgery, so it’s unclear who would take Ray’s spot in the rotation if he ends up hitting the shelf.

Tristan Beck is working his way back from surgery to repair an aneurysm in his right arm, but he allowed seven runs (six earned) over 1 2/3 innings in his most recent rehab start with Triple-A Sacramento on Friday.

Pitching prospect Mason Black struggled to an 8.79 ERA over his first four Major League appearances this year, but he’s been pitching better for the River Cats this month, logging a 2.91 ERA over four starts in August. The Giants could also lean on their bullpen to cover the spot, with Hjelle and Spencer Bivens each capable of throwing multiple innings.

“We’ll figure it out as we go, but it’s certainly not ideal,” Melvin said.

Two young outfielders -- Heliot Ramos and Grant McCray -- emerged as bright spots on Sunday after launching a pair of long homers at the pitcher-friendly T-Mobile Park. Ramos gave the Giants a quick 2-0 lead in the first inning by blasting a top-rail fastball from Seattle right-hander Bryan Woo out to left field for his 20th home run of the year.

“Even when I was in Triple-A, that was my goal,” said Ramos, who didn’t make his season debut until May 8. “I hit eight in Triple-A, so for me it counts as 28. Big leagues are the ones that actually count, but that’s always been my goal. I always wanted to do it. I’ve never had a 20-homer season. It’s been a goal of mine to be a good hitter and be that kind of hitter, for sure.”

The 24-year-old Ramos became the youngest Giants player with 20 homers in a single season since Pablo Sandoval hit 23 in 2011. He’ll need 10 more to become the first Giant to deliver a 30-homer season since Barry Bonds in 2004, but he believes he can get there.

“That’s a tough one, but I might do it, yeah,” Ramos said.

McCray added his second career homer in the eighth, hitting a misplaced cutter from Collin Snider off the right-field scoreboard for a Statcast-projected 407-foot blast that brought the Giants within one.

“He’s a really good player,” Ramos said. “He knows what he’s doing, and he knows what he wants to do. That’s my boy. I love him.”