CHICAGO -- Like all starting pitchers, Jon Lester has tunnel vision before an outing and usually concentrates solely on what he needs to do to get outs.

But, with the Chicago Cubs in the midst of a rough stretch and struggling with an overworked bullpen, the left-hander adjusted his focus before his start Wednesday to also consider what the team needed.

"There are certain games that stand out where I have to throw as deep as I can," he said. "I take the mindset every start I'm gonna throw nine (innings), but you obviously know in the back of your mind that you have to give your bullpen a breather."

Lester (6-8) struck out a season-high 14 and pitched eight strong innings to lead the Cubs to a 3-2 victory over the Colorado Rockies. He allowed two runs, five hits and one walk in his longest outing this season.

It was his third double-digit strikeout effort of the season and the 23rd of his career. He also became the first Cubs left-hander to strike out 13 or more in a game since at least 1914. The 14 strikeouts were the most by a Cub since right-hander Mark Prior had 16 against the Cincinnati Reds on Sept. 30, 2004.

"That was his best performance all year," Chicago manager Joe Maddon said. "I thought stuff-wise he had everything going on. We definitely need that (and) he supplied it. That's what guys like Jon Lester do for a team. It's a perfect example. We had some more missed opportunities and made a couple of mistakes on the bases, but he was able to right us. He righted the ship."

First baseman Anthony Rizzo and center fielder Dexter Fowler each had a home run to account for the Cubs' offense.

Right fielder Carlos Gonzalez, a subject of trade talks, hit his 21st home run and eighth in his last seven games for the Rockies. Jose Reyes, in his debut with Colorado, went 1-for-3 with a walk.

"He's in a good place. He's still rolling, and we've seen him before when he's done this," manager Walt Weiss said. "It's fun to watch. He's locked in."

The Cubs jumped on top 1-0 as Fowler led off the first with his home run.

The lead grew to 3-0 in the third on a two-run shot by Rizzo, the slugger's 17th homer of the season and first since July 7. Rizzo turned on an inside fastball from Colorado starter Eddie Butler (3-7) and managed to keep the high drive fair as it bounced off the screen on the foul pole down the right-field line.

Lester, thanks to a thrown-out base stealer in the first inning, faced the minimum through the first three innings. He struck out seven.

The Rockies, though, were able to push across a run in the fourth. Charlie Blackmon led off with a single, stole second and third (as part of a double steal with Reyes) and scored on a sacrifice fly by third baseman Nolan Arenado to trim the deficit to 3-1.

Reyes advanced to third as Blackmon scored, but Lester struck out Gonzalez swinging and second baseman DJ LeMahieu looking to end the threat.

The Rockies made it 3-2 in the seventh when Gonzalez stroked a line-drive solo homer to center on a 1-1 fastball by Lester.

The Rockies had a runner on second with two out in the eighth, but Lester got Blackmon to fly out to end the inning.

"It was nice that Joe let me go back out there for the eighth," Lester said. "It was nice to pitch into the eighth and finish the eighth."

NOTES: The Cubs placed RHP Neil Ramirez on the 15-day disabled list with left abdominal soreness and optioned RHP Dallas Beeler, who allowed four runs in 1 1/3 innings during Tuesday's start, to Triple-A Iowa. The Cubs recalled RHP Yoervis Medina and selected the contract of RHP Ben Rowen from Iowa to fill those roster spots. ... SS Jose Reyes has batted leadoff nearly all of his career, but Rockies manager Walt Weiss decided to keep CF Charlie Blackmon in that role. Reyes batted second, and 2B DJ LeMahieu moved to the fifth spot. ... Cubs CF Dexter Fowler's leadoff homer was the 11th of his career and his second this season.