"He's a Cy Young winner," Cubs manager Lou Piniella said of Lincecum (3-1). "What else do you need to say?"
Aaron Rowand added a two-run double in the eighth to hand Marshall (0-2) the loss and snap the Cubs' winning streak at four games.
Piniella wanted to give some of his regulars a day off, so his lineup included Bobby Scales, 31, called up Monday from Triple-A Iowa and making his Major League debut after 10 years in the Minors.
The Cubs also were overloaded with left-handed bats and switch-hitters, hoping to gain some kind of edge against Lincecum. However, this year, righties are hitting .277 and lefties .218 against the right-hander.
"He's good," Derrek Lee said of Lincecum. "He's obviously one of the best in the game. We got a run on him early and then he shut us down."
Lee, the lone right-handed bat in the Cubs lineup, doubled to open the second and scored on Mike Fontenot's groundout.
That closed the gap to 3-1. The Giants gave Lincecum all the runs he needed in the first on Molina's blast, his fifth, with one out. Marshall hit an RBI single with two outs in the fifth, driving in Scales, who had singled for his first Major League hit.
Marshall served up five runs on eight hits and one walk over seven-plus innings, the 20th time in 26 games that a Cubs starter has gone at least six innings. The first two Giants runners got on base in the eighth, and Jeff Samardzija replaced Marshall and plunked Molina to load the bases. Rowand then doubled, and Randy Winn added a RBI single.
Samardzija now has an ugly 8.10 ERA.
"Today, the bullpen just didn't hold the game in check," Piniella said. "Samardzija needs to work on his second and third pitches. It's hard to pitch up here with a fastball only."
Can the young right-hander do that in the big leagues?
"I hope so," Piniella said. "I talked to him when we took him out. I said when he throws his bullpen sessions, that's what he needs to work on."
Marshall needs to start treating his teammates to dinner. In his last three starts, the Cubs have scored six runs.
"That changes," Piniella said. "You keep pitching well and you'll start getting runs."
"He pitched good like he did last time," Cubs catcher Koyie Hill said of Marshall, who held Florida to one run on six hits over seven innings in his last start. "Unfortunately, every pitch counts, and the first inning, we're not going to get that pitch back [to Molina]. [Marshall] did a great job shutting them down the rest of the game. There's a lot to be said for giving up three in the first and then shutting them down the rest of the game. I was proud of him."
Marshall, who has gotten into a good rhythm with regular starts, isn't upset at the lack of support.
"That's baseball," he said. "I could be frustrated or I could bounce back from it and do better the next time."
Next time will be Sunday in Milwaukee.