SEATTLE -- After losing to the Mariners on Tuesday night, Rangers starter Jon Gray said he couldn’t wait to make his next start.

Unfortunately for Texas, he’ll have to wait a little bit longer.

The Rangers announced Thursday that Gray sprained the medial collateral ligament in his left knee in the first inning of Tuesday’s game. He will be placed on the 10-day injured list on Friday, with right-hander Glenn Otto taking his place in the rotation and starting Friday’s game against the A’s in Oakland.

Otto, 26, was 0-3 with a 9.26 ERA in six starts for the Rangers last season. He began this season with Triple-A Round Rock. Martín Pérez will start on Saturday in Oakland and Spencer Howard will come off the IL (blister) to make Sunday’s start in the series finale vs. the A’s.

“What's frustrating is not having an ability just to make back-to-back starts,” said Gray, who had just returned from another IL stint with a blister that had kept him out of action since his Opening Day outing. “But just looking on the bright side of things, it's not something serious. It’s kind of funny the way it happened, but that's just the unfortunate side of things.”

Gray said it happened right away in Tuesday’s 6-2 loss in the series opener at T-Mobile Park, in which he gave up four runs in five innings. Gray was pitching to Seattle leadoff hitter Adam Frazier, who showed bunt early in the count, prompting Gray to jump off the front of the mound. Gray landed on the left leg and said he felt it twist a bit.

He was able to complete his five innings through a touch of soreness, but he said it felt worse the next morning and went to get the MRI. Gray said there won’t be injections and that he’s hoping it’s very minor and will just cost him one start.

“We're just going to do a lot of therapy on it,” Gray said. “I'll still be able to throw. I don't know if it's going to be off a mound or not, but I’ll have the arm going. So I don't think we’re going to have a setback with pitch counts or anything like that.”

Gray said the key for the next 10 days is staying positive.

“The opportunities are coming, and they're right around the corner,” Gray said. “The start on Tuesday, it was a great time to have a great game and turn things around. I probably won't have that chance this week, but it's going to come."