NEW YORK -- Yankees pitcher Marcus Stroman went to a hospital for tests on his left knee after he gave up five runs before getting chased in the first inning of a 9-1 loss to the San Francisco Giants on a cold and rainy Friday night.

New York manager Aaron Boone had just about finished his postgame news conference when he revealed Stroman was not in the clubhouse to speak with reporters.

"He came out. His knee was bothering him, so he went to get some tests done on his knee, so we'll see what we have from there," Boone said. "He said his left knee was bugging him, so he got some X-rays here, and I think he went to the hospital to get some more testing, and so we'll see what we have tomorrow."

Jung Hoo Lee hit a three-run homer and LaMonte Wade Jr. a two-run double in the first inning as the Giants won for the ninth time in 11 games. The game was called in the top of the sixth inning after weather conditions deteriorated.

New York has lost four of five following a 6-2 start and its rotation has a 5.46 ERA, worst among the 30 teams. Max Fried has a 1.56 ERA, but Carlos Rodón is at 5.19, Will Warren at 6.00, Carlos Carrasco at 7.71 and Stroman at 11.57.

"We got to do better," Boone said. "Obviously, we're coming off a great start with Max. But we've struggled to this point. ... It's 13 games in, but we've got night in and night out to pitch a little bit better to put us in a good situation."

Stroman lasted nine batters, throwing 46 pitches and getting two outs while allowing four hits and three walks.

Clarke Schmidt is slated to rejoin the Yankees on Tuesday or Wednesday after recovering from right rotator cuff tendinitis that has sidelined him since spring training. Boone wouldn't address who would be dropped from the rotation.

Stroman's ERA would be the highest in the major leagues if he had enough innings to qualify.

"He's dotting off the plate," Boone said, "and then when he came into the zone he got hurt."

A right-hander who turns 34 on May 1, Stroman (0-1) is in the second season of a two-year contract guaranteeing $37 million. His deal includes a $16 million conditional player option for 2026 that could be exercised if he pitches in at least 140 innings this year.

He skipped the Yankees' first two spring training workouts at a time when he didn't have a projected rotation role behind Gerrit Cole, Fried, Rodón, Luis Gil and Schmidt. He arrived on Valentine's Day, eight days ahead of the mandatory reporting date.

"I won't pitch in the bullpen. I'm a starter," Stroman said, repeating "I'm a starter" seven times in a 13-second span. Injuries to Cole, Gil and Schmidt created an opportunity.

A two-time All-Star, Stroman hasn't pitched through the fifth inning this season and has a 2.04 WHIP. Batters are hitting .467 (7-for-15) against him in the first inning with four walks.

"The movement qualities are there. Again, it's less margin for error and there's probably some adjustments we can all make," Boone said. "The stuff's not much different than the first half of last season to the second half to now, so just we got to execute a little better."