Bumgarner was locked and loaded from the get-go, striking out the side in each of the first two innings. As the left-hander piled up the strikeouts, his pitch count escalated as well, forcing him to leave the game after the sixth. He allowed one run on two hits and two walks.
"It's evident he had good stuff today," Giants manager Bruce Bochy said. "We had a chance to give him a break. We had been riding him pretty hard this month."
Byrd's home run off Dan Haren provided ample support for the Giants' ace and helped San Francisco move to 5 1/2 games behind the Cubs for the second Wild Card spot. The win also kept San Francisco 2 1/2 games back of Los Angeles for first place in the NL West.
MOMENTS THAT MATTERED Byrd's blast: The newest member of the Giants clubbed his first home run at AT&T Park wearing a San Francisco uniform. After seeing two Haren fastballs out of the strike zone, Byrd found the pitch he was looking for and crushed it beyond the center-field wall. The blast extended the Giants' lead to four and was Byrd's fourth career homer off Haren.
"He just left it in the middle of the plate, and I put a good swing on it," Byrd said.
Tomlinson grand: San Francisco had a comfortable lead by the time Kelby Tomlinson stepped to the plate with the bases loaded in the eighth inning. But just for good measure, the rookie second baseman hammered a James Russell breaking ball into the left-field bleachers to make his first Major League home run a grand slam.
"That was a heck of an at-bat," Byrd said of Tomlinson's grand slam. "To get a breaking ball that was actually a pretty good pitch and to have a good path on it and keep it fair, that was awesome." More >
Start me up: Haren had his longest outing since joining the Cubs at the Trade Deadline. The right-hander gave up five runs over 6 1/3 innings, throwing 105 pitches. He served up Byrd's homer, the 29th off Haren this season, which leads the Majors. The right-hander has given up at least one home run in each of his five starts with the Cubs.
"I think it's something for him to build off of going into the next outing," Maddon said of Haren.
"I haven't held up my end of the bargain," Haren said. "I feel worse about it than anybody. The game isn't stopping, we've got games left, and I can either whine and complain and feel sorry for myself or just move on and try to be better the next time. I'll do anything for this team. I just want us to win. It's been an amazing experience so far, and I hope to contribute a little more down the road."
Glovework: With the Cubs' Dexter Fowler sidelined to nurse some minor injuries, Matt Szczur was in center, Kris Bryant made his first start in right and Kyle Schwarber caught for the first time since Aug. 6. Szczur misplayed Juan Perez's ball to center, which resulted in an RBI double, and Schwarber overthrew second base in the third trying to get Nori Aoki, who reached third on the error and then scored on Matt Duffy's single for a 2-1 Giants lead.
But in the seventh, Chris Denorfia, Addison Russell and Schwarber combined on a 7-6-2 relay to throw out Aoki at home as he tried to stretch a triple into an inside-the-park home run.
"They beat us today, they deserved to beat us today," Maddon said. "But I love that our guys understand the concept of playing down to the last drop." More >
"He was trying not to smile. He was trying to hold it in. I didn't want him holding it in. I just pointed up [to the scoreboard] so he could see himself and enjoy it. You know, you're young. You hit your first home run, it's a big one, grand slam. You've got to enjoy it, got to smile." -- Byrd, on Tomlinson
"We knew coming into this week we were facing some good starters. There are a lot of good starters. To be the same every day and come in and battle no matter who's on the mound, that's what we have to take away from this. We love competing against the best, and these guys are. More than anything, we need to learn to be ourselves and have a good plan every day and just execute it." -- Denorfia
SOUND SMART WITH YOUR FRIENDS
The Cubs lead the NL in strikeouts, and Thursday was the 10th time this season a starting pitcher has fanned at least 10 Chicago batters in a game, which matches the 2014 season total. The last time the Cubs whiffed more was 1964 (12 games).
After the game, the Cubs announced they had acquired reliever Fernando Rodney from the Mariners for a player to be named or cash considerations. Rodney, whom Maddon had on his staff in Tampa Bay, is expected to join the Cubs in Los Angeles on Friday. More >
WHAT'S NEXT Cubs:Jason Hammel will open the Cubs' three-game series at Dodger Stadium on Friday. The right-hander is coming off a win against the Braves in which he posted a quality start, his 11th of the season but first since July 3. On June 23, Hammel threw 7 2/3 shutout innings against the Dodgers, giving up two hits. First pitch is scheduled for 9:10 p.m. CT.
Giants: San Francisco welcomes the St. Louis Cardinals to AT&T Park on Friday night at 7:15 PT to begin a three-game set. Mike Leake gets the ball to open up a critical series as the Giants look to catch the Cubs for the second Wild Card spot and the Dodgers for the NL West lead.