Furbush doesn't think the situation is anything serious.
"I just felt a little tightness in the triceps that I'd never felt before," he said. "But I passed all the tests with flying colors. It could have just been that my arm was in the wrong arm slot or a variety of things. But I came in afterward and threw about 15 pitches in the cage and felt fine. It could have just been one pitch that came out weird."
Furbush pointed to his left shoulder as trainers escorted him off the mound in the seventh inning. Furbush, who relieved starter Blake Beavan with none out and runners on second and third, got Chris Getz on a groundout to second base as a run scored to cut Seattle's lead to 9-4. But it turned out to be a short night for him as the Mariners went on to a 9-6 win.
"I don't think it's anything serious," manager Eric Wedge said. "We'll see how he feels [Wednesday]. It wasn't anything we wanted to push. He felt a little tightness on that last pitch, so we got him out of there."
Furbush had Tommy John surgery in 2008, but said this wasn't anything similar.
"It was a new feeling for me," he said. "It didn't scare me, in comparison to having Tommy John, where I knew something wasn't right. Obviously doing the tests and playing catch, I felt fine. I just wanted to be cautious and stay on top of it and not have something go wrong later."
Furbush has been outstanding in a relief role this season, going 4-2 with a 2.17 ERA in 34 appearances while holding opposing batters to a .148 average. He'd allowed just 19 hits in 37 1/3 innings with 11 walks and 47 strikeouts.