CHICAGO -- After giving up 10 earned runs -- the second most in any start of his career -- Chicago Cubs left-hander Jon Lester called himself the "weakest link" in the team's rotation.

"I feel like they had a better plan than I did," Lester said Tuesday of the Oakland Athletics hitters. "Plain and simple. They executed their plan and before we could make the adjustment there's eight runs up there."

Oakland sent 12 batters to the plate during an eight-run second inning, then plated three more in the fourth on a Stephen Piscotty home run. Dustin Garneau also knocked in three with a long ball in Oakland's 11-4 win.

"What happened is I gave up 11 runs, so it doesn't matter how I feel," Lester said. "Doesn't matter about a game plan, doesn't matter about executing pitches, doesn't matter about anything. I gave up 11 runs, so it really doesn't matter."

Lester has given up 35 hits over his past four starts, and his ERA has ballooned to 4.46. He was asked about the injuries to the Cubs' bullpen but pivoted the conversation back to him.

"When it comes down to it, the injuries are the injuries, but I'm pretty much the weakest link in the rotation right now and have to figure out a way to right the ship, pick my end up, and do better," Lester said. "Flat-out do better.

"Our rotation has pitched well, except for me."

Cubs manager Joe Maddon said he didn't read much into the outing.

"Jon has been there before," he said. "This is a waste can kind of a night. You just dump it and move on."

There was one bright spot in the loss, which snapped a four-game Cubs winning streak. Reliever Duane Underwood struck out all six batters he faced in his season debut with the team.

"Out of some bad, some good occurs," Maddon said.

Added Lester: "That was impressive. He probably should have started the game."