Chicago Cubs: When is it time to worry about Jon Lester?

It’s only Spring Training, but is it time to worry about Chicago Cubs ace Jon Lester?

The Chicago Cubs pitching staff is in a precarious spot and the team isn’t even out of Spring Training yet.

For starters, Tyler Chatwood is as mercurial as they come. He can be lights out for a stretch of time until something disrupts his rhythm — then his games turn into a walkathon. He’s like the guy who hits 50 free throws in a row, so you throw the ball off to the side to make him re-set his feet, and then he can’t even hit the rim. Not to mention the Cubs appear to prefer him (at least for now) coming out of the bullpen. In other words, don’t count on much from him as a starter in 2019.

Then there’s Yu Darvish, who is always a stiff breeze away from an extended trip to the IL, so to count on him as a reliable option in 2019 seems risky as well. The better approach appears to be to manage expectations and be pleasantly surprised if he returns to the form that led the Cubbies to give him his massive contract.

With two key rotation members so up and down — and frankly unreliable — the Cubs will once again count on old reliable, Jon Lester to be the stopper the team desperately needs. He filled that role valiantly last season and almost willed the team into the playoffs.

However, Lester’s struggles this spring, combined with some data, suggests there could be problems ahead for the 35-year-old lefty.

As Cubs fans have likely noticed, Lester has been getting hit pretty hard thus far in Spring Training. Under normal circumstances, that wouldn’t be a huge cause for concern, as pitchers are still building up arm strength, tinkering with mechanics, and location, and getting themselves into form for opening day. No pitcher is worried about their statistics in the spring as long as they feel they are on track to be ready for the regular season.

However, there are certain numbers Lester is putting up this spring that should be cause for concern, especially when viewed in light of some recent trends. First and foremost, Lester is 35, so naturally, there is going to be some regression.

His strikeout to walk percentage has been on a steady decline over the last four seasons. In short, hitters are making more contact against Lester, and he’s not able to rely on plus stuff to get out hitters. As you’d expect his hard hit percentage has also risen each year during that span — climbing nearly six points between 2017 and 2018. According to FanGraphs, what saved Lester last season was his outstanding left-on-base percentage (80 percent).

The above trends (with the exception of the left-on-base percentage) are likely to continue this season since Lester’s velocity appears to be declining as well. Last year, his four-seamer averaged over 91 mph. For comparison, in his last outing against the Colorado Rockies, he topped out at 91.7 and averaged only 89.5 mph.

Declining velocity combined with the reality that his left-on-base percentage will most likely come down some seems like a recipe for a much higher ERA this season. However, the good news is Lester historically has evolved his game. He realizes he can no longer purely rely on his stuff and must be precise in his location.

While there is definitely cause for concern heading into the season, if anyone can make the necessary adjustments to continue to pitch at a high level, it’s Lester.