They also carried the Orioles to a mark of seven games over .500, keeping the team in the thick of a Wild Card race many pundits expected they would have dropped out of long ago.
Maybe the biggest key in the team's recent three-game surge has been dominance on the mound. Before Tillman finally yielded a run in the eighth, the O's pitching staff ran its shutout streak to a season-long 28 consecutive innings.
Tillman exited to a standing ovation in the eighth, allowing just one run on five hits and a walk over 7 1/3 frames.
"He's been able to use all of his pitches," catcher Matt Wieters said. "When he can work off four, it's going to give him a chance to succeed. Tillman has the right attitude. He doesn't think too much. He keeps moving forward. He keeps working and trying to improve."
That work ethic and continued growth will serve Tillman well in what manager Buck Showalter called "an ongoing proving ground."
In six starts since being called up from Triple-A Norfolk, Tillman is 5-1 with a 2.38 ERA -- numbers artificially inflated by the fact that he allowed only one earned run and six unearned in 2/3 of an inning on July 16 against Minnesota.
The right-hander was a far cry from that dud on Monday, throwing 68 of his 99 pitches for strikes and allowing just one three-ball count.
"I feel like I put in a lot of work in in the offseason, and carried it into the season and Spring Training," Tillman said. "It's starting to pay off here, and we're not done. We have a long way to go. We've got a lot of season left and we've got to keep working until we're done."
Perhaps Tillman's biggest hurdle was getting through the first inning, where 13 of the 18 runs against him have been scored this season. The opening frame -- and beyond -- proved to be no issue on Monday, as Tillman retired the side in order over the first three innings.
The right-hander did not allow a baserunner until Michael Saunders drew a one-out walk in the fourth and did not allow a hit until Mike Carp grounded a single through the O's defensive shift with one out in the fifth.
"I went out with the mindset of one inning at a time," Tillman said. "[The first inning] has been kind of a downfall for me, but I knew what I needed to do to get through it and I made some pitches."
After pitching around leadoff hits in the sixth and seventh, Tillman finally allowed a run in the eighth. Eric Thames led off with a double and scored on a single from Munenori Kawasaki, ending Tillman's night.
In three career starts against the Mariners -- the team that drafted him and later traded him to the O's -- Tillman is 3-0 with a 0.83 ERA.
"Knowing Chris, he doesn't belabor that," Showalter said. "He's just trying to establish himself and give us a chance to win, not in that order. Chris likes to win. He likes for us to do well. He's got a quiet burn there. He doesn't back off the competition."
"I kind of got over [the trade] after that '08 season when I came over here," Tillman said. "Just another team to go out there and give my team a chance to win."
Although Tillman's fastball typically sat two or three miles per hour below his usual average of 93, the righty used strong command and a good changeup to blow through Seattle's lineup.
"My changeup's been there for me all year, and I think that came into play tonight," Tillman said. "The more you throw the changeup, the harder the fastball's going to look. I think the changeup got me through that game tonight."
"His curveball had a really good bite in the early innings," Mariners outfielder Eric Thames said. "The ball would start at your chest, and you'd swing in the dirt. A big 12-6. 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 pitch. Just one of those days."
The O's scored all three of their runs in the second inning against Mariners starter Jason Vargas, who allowed eight hits in an eight-inning complete game.
Lew Ford led off the second by flaring a single to left and scored when Mark Reynolds drilled a double to the gap in left-center for only his second RBI since July 20.
"It was kind of just one pitch," Vargas said. "That pitch to Reynolds I left over the plate allowed them to extend the inning."
Nick Markakis pushed the Orioles lead to 3-0 with a two-run homer to right, continuing his tear since moving to the top of the order. In 24 games batting leadoff since returning from the disabled list with a fractured right hamate bone, Markakis is hitting .346 with three home runs and eight RBIs.
Reynolds finished the game 3-for-3 with a pair of doubles for just his fourth game with three or more hits this season.
"I'm not relieved," Reynolds said. "I've been working my butt off with [hitting coach Jim Presley] in the cage, early BP and just trying to figure this thing out. It's nice to see some results, but it's just one night."
Just one night for Reynolds, just one night for Tillman and just one more night for the Orioles. But at least it was a good one.