Having survived a 16-game stretch without Sammy Sosa, the Orioles must now do without catcher Javy Lopez, who will be sidelined for about six weeks with a broken bone in his right hand.
There's also some question about the health of leadoff hitter Brian Roberts, who hobbled off the field with a bruised knee.
And so, even though the first-place Orioles lengthened their lead in the AL East to three games with a 3-2 victory Tuesday night, there was little to celebrate.
"Hopefully, we'll be resilient," manager Lee Mazzilli said. "You lose a guy and it's a tough blow, but what are you going to do? You've got to go out and play, and that's what we're going to do."
Jay Gibbons, who hit the tiebreaking home run in the eighth inning, said, "Everybody has to deal with injuries. Fortunately I think Brian is OK, but Javy is hurt. We're going to have to fill the void at the catching position and offensively."
Melvin Mora had three hits and drove in a run for the Orioles, who stranded 13 runners but got the clutch hits they needed late.
After Baltimore pulled even in the seventh inning, Gibbons hit a solo shot to center off J.J. Putz (1-1) to give the Orioles their first lead.
"He hit a ball that was down and got it up," said Seattle manager Mike Hargrove, returning to Baltimore for the first time since being fired as the Orioles' manager in 2003.
Todd Williams (4-3) worked the eighth, and B.J. Ryan got three outs for his 13th save.
Mere hours after activating Sosa from the 15-day disabled list, the Orioles lost Lopez, who was hit on his non-glove hand by a foul tip off the bat of Bret Boone in the third inning. He will be placed on the disabled list Wednesday.
"Knowing that I'm going to miss at least six weeks is pretty frustrating, especially when I'm starting to feel good with the bat and right when Sammy came back to the lineup," Lopez said. "I've been hit by foul tips before, but this is the first time I broke a bone."
Baltimore also received a scare when Roberts was hit in the left knee by a pitch from reliever Ron Villone in the seventh. Roberts remained on the ground for several minutes before taking his base, but left after reaching second on a grounder.
He will be evaluated Wednesday.
After Roberts left, the Orioles loaded the bases before Sosa hit a sacrifice fly off Jeff Nelson to make it 2-all.
Sosa went 1-for-2 with a walk and an RBI as the designated hitter. He missed most of the month with a staph infection under his left foot.
Richie Sexson drove in two runs and Ichiro Suzuki went 3-for-3 and scored twice for the Mariners, but that was the extent of the Seattle attack.
The Orioles received a solid performance from starter Bruce Chen, who gave up two runs and eight hits in seven innings.
Seattle starter Joel Pineiro, recalled earlier Tuesday from Triple-A Tacoma, allowed one run and five hits in 5 1/3 innings.
"What I did (in the minors) paid off to get me ready for my start," the right-hander said. "Being myself, being more aggressive, getting things in my head I didn't do last year."
After Pineiro left, Villone retired B.J. Surhoff on a groundout, then got Gibbons to fly out with runners on second and third.
Gibbons later made amends with his eighth homer.
Seattle got a run in the first inning when Suzuki singled and scored on a two-out single by Sexson.
In the bottom half, Orioles rookie Jeff Fiorentino walked and got his first major league stolen base before scoring on a single by Mora.
Suzuki led off the third with a walk, stole second and scored on a single by Sexson.
The start of the game was delayed 18 minutes by rain. ... Roberts extended his hitting streak to 14 games, tying a career high set earlier this season. ... Chen allowed the leadoff hitter to reach in six of his seven innings. ... It was Suzuki's 19th multihit game.