The lefty tossed 8 1/3 scoreless innings, giving up six hits. He walked two and struck out three.
"I mean, my motivation is kind of the same every game," said Lester. "I want to try to finish every game that I can. Obviously these guys had a long day. [I was] fortunate enough to come in yesterday. I think for us to come in with that travel schedule, which guys aren't normally accustomed to, and do what we did tonight, it's big for us."
It was just the type of pitching performance that his team needed. After losing to the Yankees in a Sunday night game that ended after midnight ET, the Red Sox rose up Monday morning and flew out of Boston at 10:20 a.m.
Most of the team went straight to the ballpark after the six-hour flight touched down in San Francisco.
"Anytime you have these long travel days, you always look to the starting pitcher to keep the game under control," said manager John Farrell. "Not knowing how you're going to come out physically from an offensive standpoint, how many different times you can push to get an offense started, he gave us just that."
Though the Red Sox had to be tired after a long day, they didn't let it impact their performance.
The offense, led by three hits from Shane Victorino and Daniel Nava, plus multi-hit performances from Stephen Drew and Jarrod Saltalamacchia, gave Lester enough to work with on a night he outpitched Tim Lincecum.
"We played great," said Dustin Pedroia, who had a triple. "Jon, he was unbelievable. It seems like we were barely on defense. He was getting us back in swinging the bat. Guys had great at-bats. It was a big win."
The victory was much needed for a Boston team that had lost seven out of 10.
With the Rays defeating Baltimore, the Red Sox held on to their one-game lead in the American League East.
The bats rallied against Lincecum in the second. Saltalamacchia led off with a single to right. Nava drew a walk. Drew's single loaded the bases with nobody out. Will Middlebrooks did his job, lofting a sacrifice fly to right for the first run of the game. Nava wound up scoring on a balk and Victorino capped the rally with an RBI single to make it 3-0.
"To get on the board, however it happens, is key. When we score first I think it has the ability for us to take a breath a little bit," Farrell said.
While Lester stifled the Giants, Drew extended Boston's lead to four runs by belting a two-out, RBI double to right-center in the fifth.
Jacoby Ellsbury scored the fifth run on reliever Guillermo Moscoso's wild pitch in the sixth, and Pedroia tripled ahead of Saltalamacchia's RBI double in the ninth. Saltalamacchia scored on Nava's third single of the night.
After a lull immediately following the All-Star break, Nava is starting to recapture his early-season form, when he was one of Boston's best hitters.
"Looks like he's got his legs back underneath him, and I mean that by we gave him a few days down to renew physically," said Farrell. "And when he gets fatigued, you see the swing get a little long, but that's not been the case over the last five to seven games he's been in there. A lot of hard contact."
Though there were nice contributions across the board, the story of the night, without question, was Lester.
"He moved the ball around both sides of the plate, mixed in four pitches and attacked the zone," said Giants catcher Buster Posey.
After getting former teammate Marco Scutaro to ground into a double play to end the eighth, Lester hollered, "I'm finishing this game" as he walked off the mound.
Farrell gave him the chance, but Lester gave up back-to-back one-out singles to Posey and Hunter Pence.
Brandon Workman finished the game, but Lester's performance was still more than good enough.
"Jon was exactly what we needed -- we needed a strong pitching performance on a night when we could use a guy to go deep in the game and he gave us just that," Farrell said. "An outstanding effort on his part. A lot of strikes, I thought his fastball was sharp, it was powerful and he mixed in some breaking balls and particularly his cutter was powerful tonight."
Lester, who had a prolonged rut in the middle of the season, is starting to pitch like an ace again at just the time his team needs him to.
Since the All-Star break, Lester is 3-1 with a 2.52 ERA and that includes a start in which Arizona shelled him for six runs.
"Arizona was just bad everything. Not a good game," said Lester. "But I feel like after the break, I've thrown the ball really well. I just keep trying to build off of each positive start and I'll try to build off today."