The Baltimore Orioles' right-hander departed with a one-run lead, but the bullpen gave up two runs in the eighth — one on Erick Aybar's RBI double against Tommy Hunter, the other on a bases-loaded walk to Kole Calhoun from lefty Brian Matusz.
And just like that, the AL East leaders were saddled with a 3-2 loss that reduced their division lead to three games and prevented them from sweeping the Angels in a three-game series for the first time since 2010.
"They've got a good lineup," Tillman said. "They are going to battle all night long, all series long. It never felt like you had the game in hand. They grinded me out tonight, put some real good at-bats together. Sometimes you've got to tip your cap."
Josh Hamilton led off the eighth with a bloop single off Hunter (2-2) and came all the way around on Aybar's hit to left-center. A two-out intentional walk to Efren Navarro and another walk to Chris Iannetta loaded the bases for Calhoun, who walked on Matusz's 3-1 pitch.
"I don't think it really got away from me. I thought I pitched pretty well," said Hunter, who hadn't allowed a run in his previous 12 appearances. "I didn't feel like I was just missing. I felt like I was making pretty quality pitches and they just didn't swing at them. They got a hit and a couple of walks. That's the way the story unfolded tonight."
The Angels, who came in leading the majors in runs scored, stranded two runners in scoring position in the first, fifth and sixth innings. They Angels were 0 for 12 in those situations overall on Wednesday, and 3 for 25 during the three-game series.
Tillman allowed a run and five hits and picked off Iannetta at second base with Mike Trout at the plate to end the second inning. But for the eighth time in Tillman's last 11 starts, his teammates the Orioles failed to score more than two runs while he was in the game. So there has been much less room for error.
"I feel like a lot of the games are going to be that way now," he said. "We are coming to the part of the year where everyone kind of sees the light at the end of the tunnel to get to where they want to be in the postseason. So I think it's good if that's the way it's going to be. That's the way it should be. Hopefully, we can come out on top."
Jered Weaver (11-6) allowed two runs and six hits through eight innings, striking out six and walking none before the Angels recorded their major league-best 31st come-from-behind win. The right-hander won his fourth straight decision.
Huston Street pitched a hitless ninth for his first save since joining the Angels last Friday in a trade with the San Diego Padres.
Baltimore took a 2-1 lead in the sixth when David Lough singled with two outs, stole second and scored on Adam Jones' flare to short right field. Eight of the Orioles' 10 runs in the series came with two outs.
Ryan Flaherty, starting at third base for the second straight game because of Manny Machado's stiff back, made a diving backhanded stop of Trout's first-inning grounder behind the bag but couldn't get the throw to first in time. Trout scored on Albert Pujols' single high off the 18-foot wall in right-center.
"That's a do-or-die play with him," Flaherty said of Trout's infield hit. "When he hits a ball like that. You've got to hope he trips in order to get him out."
Pujols' RBI was his 31st in his last 34 games and 66th this season. The three-time NL MVP had at least 100 RBIs in 10 of his first 11 big league seasons. The only exception was 2011, when he had 99.
"Albert's important to us. We don't need him to carry us, but we need him to do what he's capable of. And we're seeing it," manager Mike Scioscia said. "Albert's last 50 at-bats, I think you're able to see that he's been able to use the whole field and he's finding that swing. Tonight he drove the ball to right-center to score Mike and then hit a double down the line."
The Orioles tied it in the third on a two-out RBI single by Nick Markakis after Flaherty hit a ground-rule double and tagged up on Nick Hundley's fly ball.
NOTES: J.J. Hardy was 0 for 3 against Weaver and has two hits in 20 career at-bats against him. ... Pujols' cousin, former major league catcher and coach Luis Pujols, currently manages the Orioles' Single-A Carolina League farm club in Frederick, Maryland. ... Tillman's 32 victories since July 4, 2012 are the second-most in the majors behind reigning AL Cy Young Award winner Max Scherzer — whom the Angels are scheduled to face Thursday night in the opener of a four-game series with Detroit.