Right-hander Duane Underwood Jr. tying a team record for consecutive strikeouts by a reliever with six was a positive.

Seeing catcher Taylor Davis throw a scoreless ninth inning with Kyle Schwarber behind the plate was worth a chuckle and injected some late life into Wrigley Field.

But those two stories were sidebars to left-hander Jon Lester’s night in an 11-4 loss Tuesday to the Athletics that ended the Cubs’ four-game winning streak.

Lester surrendered 11 runs (10 earned) and 10 hits in four innings in one of the worst starts of his accomplished career. He allowed eight runs (seven earned) and six hits, including a three-run home run to Dustin Garneau, and faced 12 batters in the second. Things got no better when he allowed a three-run homer to Stephen Piscotty in the fourth.

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

But Lester’s performance and the starting rotation as a whole matter more than ever for the Cubs.

Their offense has sputtered all season, especially against left-handed pitching, and will be without All-Star catcher Willson Contreras (hamstring) for at least a month. Their bullpen is trying to make do without expensive closer Craig Kimbrel (knee) and standout setup man Brandon Kintzler (pectoral), who went on the injured list Tuesday.

‘‘The rotation, it’s hard to ask for more out of this rotation than they’ve given at this point,’’ manager Joe Maddon said. ‘‘You just let them go out there and play. I’m not going to ever insinuate to any of them that we need more out of them. It is what it is. Go pitch, do your best and let us try to figure it out.’’

Even if Maddon didn’t say so, it might be up to the rotation to win a tight National League Central race. At least recently, four of the Cubs’ starters have been pluses for what might be a frantic race to the end.

Left-hander Jose Quintana has won five consecutive decisions. Right-hander Kyle Hendricks leads the team with 12 quality starts and allowed only one hit in 6„ innings Monday. Left-hander Cole Hamels returned from the IL and threw five scoreless innings Saturday. Much maligned last season, right-hander Yu Darvish has struck out 44 and walked only two in his last six starts.

Then there’s Lester, who has given up 15 earned runs in his last nine innings and has seen his ERA swell to 4.46. He was honest about his recent results and blunt when assessing where he stacks up with the rest of the starters.

‘‘When it comes down to it, I mean, the injuries are the injuries,’’ he said. ‘‘But I’m pretty much the weakest link in the rotation right now, and I’ve got to figure out a way to right that ship. Pick my end up. Do better. Flat-out do better.’’

For the Cubs to survive their bullpen issues and win the NL Central for the third time in the last four seasons, they likely will need more from Lester.

‘‘At the end of the day, our rotation has pitched well except for me,’’ he said.

Perhaps Lester’s biggest contribution Tuesday was lasting four innings and throwing 94 pitches to save — at least to some degree — a taxed bullpen.

‘‘Jon’s been there before,’’ Maddon said. ‘‘This is a waste-can kind of night, and you just dump it and move on.’’