The lanky right-hander, who pitched the clinching game of the World Series for the St. Louis Cardinals last fall, was poised for his first win Thursday against the Cubs. But reliever Brandon Morrow faltered and Cesar Izturis' two-run double rallied Chicago to a 5-4 victory.
Weaver, who entered the game winless in six decisions with a 12.46 ERA, gave up three runs in the first but held Seattle without another run over the next five innings.
"Other than (the first inning), I was really happy with execution of the pitches and it's another step in the right direction," Weaver said.
Seattle led 4-3 in the eighth when Morrow (3-1), who earlier this month had a string of 18 2/3 innings scoreless innings snapped, walked the first two batters he faced. Koyie Hill sacrificed them to second and third before Izturis hit a liner down the left field line to put the Cubs ahead.
Bob Howry (3-3) got the final four outs for the win.
Weaver's season has been defined by the big inning. The Cubs' first marked the seventh time this season that Weaver had allowed at least three runs in an inning.
In his last start five days ago -- his first since coming off the DL with a sore shoulder -- Weaver was forced out after four innings with lower back stiffness.
"When we got past the first inning, everything improved. His stuff, his command, everything," Mariners manager Mike Hargrove said. "We got a real good outing out of him."
After struggling most of the season in close games, the Cubs have won three of their last four by one run.
"I think it's starting to reflect more confidence here," Cubs manager Lou Piniella said after his team took two of three from the Mariners. "We weren't winning these games earlier in the year. ... You've got to win the tight games."
Izturis, whose playing time has been reduced by his own struggles and the switch of Ryan Theriot to shortstop, got the start Thursday. He entered the game 6-for-37.
"I always come to the ball park ready to play. On the bench, I'm ready. You got to be ready anywhere," he said.
Cubs starter Jason Marquis was cruising with a one-hit shutout into the sixth inning. But after getting the first out, he plunked Weaver near the right elbow with a pitch, and that got the Mariners going.
Marquis, who hasn't won since May 9, allowed only two hits and four runs -- three earned -- in 5 1/3 innings.
"I got to attack Jeff Weaver a little better, obviously," Marquis said. "The pitch just got away from me."
Ichiro Suzuki followed with a walk before Jose Lopez hit a grounder that Cubs third baseman Mark DeRosa mishandled for an error to make it 3-1. Jose Guillen drew a walk to load the bases before Raul Ibanez cleared them with his double to the gap in left center, giving Seattle a 4-3 lead and finishing Marquis.
After Guillen raced across with the go-ahead run, he ran into home plate umpire Tim McClelland, whom replays showed shook his finger at Guillen. Guillen went back to argue with the umpire before Hargrove came out to intercede. Guillen was not ejected and replays appeared to show his momentum carried him into McClelland and the contact was inadvertent.
"I just kept running. When I put my head up, I saw him right there," Guillen said. "I just tried to put my hand up like I was going run into him. I don't know if I pushed too hard, but I was just going in the same direction that he was. ... I'm sorry about hitting him if he thinks that was my intent. But that's never gone through my mind. ... He just kept going with 'Why'd you push me? Why'd you push me?"'
McClelland declined an interview request but said through an umpires' clubhouse attendant: "It was nothing."
Alfonso Soriano ended an 0-for-21 skid with a leadoff double in the first and scored on Felix Pie's triple to right center. One out later, Cliff Floyd hit an RBI single and chugged around on Mike Fontenot's triple into the right field corner for a 3-0 lead.
- The Mariners have won 9 of 12 after dropping two of the three to the Cubs in their first-ever trip to Wrigley Field. Seattle managed only three hits Thursday.
- Weaver and Soriano were Yankees teammates in 2002 and 2003.