Robbie Ray leaves SF Giants’ game vs. Mariners with hamstring injury

When the Giants traded away Alex Cobb and Farhan Zaidi declared their starting rotation the best in baseball, they were betting the five-man group as assembled could carry them the eight weeks from the trade deadline to the last day of the regular season and, they hoped, into October.

It was a risky wager, with a pair of rookies and another coming off major surgery, and the chances of it paying off took another blow Sunday afternoon when Robbie Ray winced and grabbed at his left hamstring on his 62nd pitch of their series finale against the Seattle Mariners.

Ray was removed from the game after a brief consultation on the mound with manager Bob Melvin and trainer Dave Groeschner, and the Giants later said he was diagnosed with left hamstring tightness.

The 32-year-old left-hander should undergo tests in the coming days that determine the severity of the injury and what kind of loss the Giants can expect in their rotation.

Prior to his exit, on the first batter of the fourth inning, Ray had overcome more difficulties finding the strike zone to allow the Giants to build a 2-1 lead. He issued three walks and hit a batter but allowed only one run, after the first of four Mariners stolen bases put Dylan Moore in position to be singled home by Cal Raleigh in the first inning, cutting the Giants’ lead to 2-1.

Heliot Ramos opened the scoring in the top of the first with his second home run of the series and his 20th of the season, becoming the first Giants outfielder 25 years or younger to reach that mark since Chili Davis in 1981.

After Tyler Fitzgerald used his speed to force a poor throw from third baseman Josh Rojas to lead off the game, Ramos unloaded on a letter-high fastball from Mariners starter Bryan Woo, an Alameda High alum, for a majestic two-run shot over the visitors’ bullpen.

Barely two innings later, Sean Hjelle was racing to warm up on the same real estate as Ray walked back to the third-base dugout.

The Giants’ bullpen wasn’t in great shape entering Sunday after Blake Snell lasted only three innings in Saturday’s 4-3 win. Closer Ryan Walker was unavailable after being used the previous two nights, and their ordinary long man, Spencer Bivens, had already been used in the same role behind Snell the previous night.

Additionally, Jordan Hicks reported some discomfort in his arm while warming up Friday night and displayed diminished velocity during his inning Saturday.

Ray was making his first start against the Mariners since they traded him to San Francisco for Mitch Haniger and Anthony DeSclafani this past winter. In seven starts for the Giants since returning from Tommy John surgery, Ray has been dominant at times but erratic at others.

In his return to Seattle, Ray issued at least three walks for his fourth time this season while failing to make it out of the fifth inning for the third time. Two starts ago, he walked five and didn’t make it out of the first inning but followed that up with his longest start since surgery, limiting the White Sox to one run on three hits while striking out nine without walking a batter.

Should he require a stint on the injured list, the Giants don’t possess anything close to the known quantity of Cobb — who made two starts in Cleveland and was placed on the IL — but have a number of options at Triple-A Sacramento, including Landen Roupp, Mason Black and Trevor McDonald, who are all already on the 40-man roster.