Chicago Cubs: When do you start worrying about Jon Lester’s struggles?

After a superb first-half showing, Chicago Cubs left-hander Jon Lester has fallen flat since the All-Star Break. When do we start to legitimately worry?

Right up till the Midsummer Classic, Jon Lester pitched like a true ace. He led the Chicago Cubs to the league’s best record, earning his fifth career All-Star selection. In mid-July, he looked likely to crack 20 wins for the first time in his big league career.

But, suddenly, things took a turn for the worse. After cruising through his first 19 outings to the tune of a 2.58 earned run average, something changed. In his four second half starts, the three-time World Series champion carries a bloated 8.53 ERA to go along with a 1.895 WHIP.

His strikeout rate is down and walk rate is up. After serving up 13 home runs in 111 innings and change, he’s already allowed six in just 19 frames since the break. Given the up-and-down efforts put forth by the rest of the staff, an erratic and ineffective Jon Lester is a major concern for this team as they chase a third-straight division title.

Chicago Cubs: Lester knows something’s not right

After the rival St. Louis Cardinals shellacked Lester for eight runs in late July, he, per usual, took the blame and mentioned an ongoing effort to make some mechanical adjustments in his delivery.

“You know, I don’t want to chalk this up as bad days happen,” said Lester. “I think mechanically this has kinda been coming.”

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After turning in three seven-inning starts in the month of June, the left-hander has failed to accomplish that feat once since then. His last coming on June 20 in a 4-0 win over the Los Angeles Dodgers.

His three starts to close out July were particularly worrisome. He totaled just 14 innings between the three times out, due largely in part to opponents lighting him to the tune of an 8.36 ERA and .321 average.

He struck out only 11, walking eight – another trend that’s emerged as the season has continued. He’s not getting the swing-and-miss putaway pitches when he needs them. Opponents are battling – and winning – far more often than we saw earlier in the campaign.

“I’ve been getting outs,” Lester said after that July 20 start against St. Louis. “I just feel like when I’ve had that strikeout or I have a guy set up for that pitch I haven’t been able to execute it.”