The Mariners failed to get a hit off Tillman until Mike Carp's single to left field with one out in the fifth. Carp started the game after flying back from California following the birth of his daughter, arriving about 90 minutes before the first pitch.
Kawasaki, starting for the second straight day in place of injured shortstop Brendan Ryan, went 2-for-3 with a bunt single in the sixth and his RBI single in the eighth after Eric Thames had doubled.
But Kawasaki was thrown out at second trying to take the extra base and the Mariners couldn't close the gap against Baltimore's bullpen once Tillman was replaced.
"In that situation, that's the game, trying to drive in the runner," Kawasaki said through interpreter Antony Suzuki. "That's all I had in mind, to drive the ball to center field and get the runner in. But then it was a bad judgment around first base in trying to get to second. I regret that, because that's where you want to gain that momentum and I wasn't able to get that, so that was unfortunate."
No disagreement there from Wedge.
"That one hurt us," said the skipper. "Great job on the base hit, but as soon as he sees that throw low on line like that, he has to put on the brakes and stay at first base."
The Mariners have still won eight of their last 11 games and are 15-8 since the All-Star break, but are off to a 1-3 start on their nine-game road trip.
Tillman, 23, is 3-0 with a 0.83 ERA in three career starts against the Mariners, who are batting .133 in 75 at-bats over 21 2/3 innings against the young right-hander. Tillman held Seattle to a pair of unearned runs and two hits over 8 1/3 innings in a 4-2 win at Safeco Field on July 4.
"His curveball had a really good bite in the early innings," said Thames, who had Seattle's only extra-base hit with his double in the eighth. "The ball would start at your chest, and you'd swing in the dirt. It's a big 12-6 curve. His fastball had good life up in the zone, and a good changeup. All his stuff was pretty much on. Whenever we were sitting on pitches, he threw the opposite. Just one of those days."
Tillman improved to 5-1 with a 2.38 ERA in six starts since being promoted from Triple-A. He said facing the team that drafted him in the second round in 2006 doesn't even enter his mind now.
"Not anymore," he said. "I kind of got over that after that '08 season, when I came over here. It's just another team to go out there against and give my team a chance to win."
Mariners lefty Jason Vargas, the American League Pitcher of the Month in July, saw his personal five-game winning streak snapped as he fell to 12-8 with his first loss since June 20.
Vargas pitched all eight innings for Seattle and only gave up three runs in the second inning on an RBI double by Mark Reynolds and two-run home run by Nick Markakis with two outs.
Vargas said it really wasn't even one bad inning that got him in this game.
"It was kind of one pitch," he said. "That pitch to Reynolds I left over the plate allowed them to extend the inning. Markakis hit a curveball I kind of hung over the plate a little bit, but that all could have been avoided if I executed to Reynolds."
Vargas has allowed 26 home runs this season, tied for the most in the AL, but Markakis' shot was the first he'd given up in his last four starts.
The 29-year-old southpaw settled in after that inning, giving up just three more hits over the final five frames and retiring eight straight Orioles on ground outs at one stretch. Vargas finished with 16 groundball outs, six flyouts and two strikeouts.
"They were hitting the changeup on the ground," Vargas said. "That's really the pitch they were putting in play for me, so we kept throwing it."
The Mariners had a chance in the ninth when Kyle Seager and Casper Wells reached on infield singles, but Thames grounded out on a hard shot to short to end the threat as Orioles closer Jim Johnson notched his 33rd save.