By TIM BOOTH

AP Sports Writer

SEATTLE (AP) - New York Yankees designated hitter Matt Carpenter broke his left foot Monday night when he fouled off a pitch against the Seattle Mariners and will be out indefinitely.

Carpenter, wearing a protective boot in the Yankees' clubhouse after their 9-4 win, said he's hopeful he might only miss a month. But a timeline won't be determined until he sees a foot specialist.

“I don’t want to say a number because I just don’t know, but I’m holding out hope that it’ll be a situation where I could come back in the middle of September and can contribute towards a stretch run,” Carpenter said. “So we’ll see. I mean, that’s my mindset is that I’ll be back.”

Carpenter fouled a slider from starter Logan Gilbert off the foot in the first inning. The left-handed hitter was briefly checked by manager Aaron Boone, but finished the at-bat and struck out swinging on the next pitch.

“I knew something was wrong when I did it, but I thought that I could finish the at-bat, get that run in,” Carpenter said. “But then when I went to swing on the next pitch, I mean as soon as I started to plant and rotate on that back foot, my lower body gave out and I wasn’t able to.”

Boone said he was immediately aware something was wrong and he knew a change was needed when he checked on Carpenter in the clubhouse between innings. Tim Locastro replaced Carpenter in the third.

“I knew he got it good. That’s why I went out there initially,” Boone said. “And I was just like, the way he was moving, I’m like, this isn’t good."

The three-time All-Star was one of the feel-good stories in baseball this year while enjoying a comeback season at age 36. Carpenter was toiling at Triple-A when the Texas Rangers released him in May. He signed with the Yankees and became a big surprise, earning regular playing time in a powerful lineup.

Carpenter began the night hitting .307 with 15 home runs and 37 RBIs in just 127 at-bats. He batted below .200 in each of the previous two seasons with St. Louis.

“He's definitely going to be missed for however long it’s going to be, but we’re hoping that we get some good news and that it’s not going to be season ending," Yankees third baseman Josh Donaldson said.

It was the latest significant injury for the Yankees, who snapped a season-worst five-game losing streak Monday night. All-Star slugger Giancarlo Stanton and pitchers Luis Severino, Michael King and Miguel Castro all went down last month and haven't returned yet.

King will miss the rest of the season with a broken right elbow, while Severino (right lat strain) and Castro (right shoulder strain) are also on the 60-day injured list. Stanton is on the 10-day IL, retroactive to July 24, with left Achilles tendinitis.

New York has the best record in the American League at 71-39 and leads the AL East by 10 1/2 games.