Castellanos got hit in his left hand with a pitch Saturday and the team is calling it a "finger contusion".
Robinson Cano chased Fulmer from the game in the fifth when he hit a 3-run home run to make it 6-2 Seattle.
X-rays came back negative, and Castellanos is day-to-day. They didn't say anything about how long I might be out, but it is broken bad, so there might be surgery, " Cano said after the Mariners' 5-4 loss to the Tigers.
Also in the second game, Tigers manager Ron Gardenhire was ejected in the bottom of the fifth inning by plate umpire Carlos Torres.
John Hicks and Pete Kozma each had two RBI to lead the Tigers in the second game. Detroit is nowhere near full strength heading into Sunday's matchup with Seattle's James Paxton, who threw a no-hitter at Toronto in his previous start.