CHICAGO -- Jon Lester does not pull punches, especially when it comes to self-evaluation. It came as no surprise, then, that the Cubs' grizzled veteran pitcher issued a blunt two-word response, and repeated it, when asked to sum up his performance at the end of last season.

"Not great," Lester said. "Not great."

No one is harder on Jon Lester than Jon Lester. And while he may have headed into the offseason wanting more out of himself, know that the Cubs have been thrilled with what Lester has accomplished on the field in their uniform and for what he has meant to the franchise since coming aboard as a free agent five winters ago.

When Lester agreed to sign with the last-place Cubs at the Winter Meetings in San Diego ahead of the 2015 campaign -- a decision that had the team's decision-makers celebrating in the lobby bar at the Manchester Grand Hyatt -- it was the first step in moving out of a rebuild and into World Series contention. With the Winter Meetings at the same site last month, Chicago's front-office team could not help but reminisce.

"We've had quite a few discussions," Cubs president of baseball operations Theo Epstein said, "just about what a great job he's done living up to that contract and then some. And how important he's been to all the good things that have happened the last five years. The big games that he's pitched for us, and the consistency that he's given us.

"And the fact that he's still a vital member of the team going into the last fully-guaranteed year of that deal says a lot about him and his work ethic. If you ask him, I think he's holding himself to the same standards that he always does."

Looking back

It would be hard for the Cubs to have asked for any more out of Lester within the first five seasons under the six-year, $155 million pact he signed with the club.

Dating back to 2015, Lester has gone 74-41 with a 3.54 ERA in 159 starts. He's averaged 15 wins, 180 strikeouts, 188 innings and 32 starts per year. He's started four Opening Days, made two All-Star teams and finished second in National League Cy Young Award voting once. He's pitched in 12 postseason games, taking the ball in a Game 1 five times and one Wild Card Game.

Oh, and Lester helped end the Cubs' 108-year World Series drought.

"He hates losing. He wants to win," Epstein said.

And that, really, is why Lester was more grouchy than usual when the 2019 season concluded. The Cubs missed the playoffs for the first time since the lefty joined the fold, and he ended with a 6.09 ERA over the final two months of the season. His innings total (171 2/3) was his lowest since 2007, and his ERA (4.46) was the highest it's been since '12.

"I think sometimes when you get into the position that I’m at, as far as in my career," Lester said, "you start kind of buying into having to change. And I don't think I had to change. I think change sometimes can be bad, and I think it put me in a bad position for most of this season."

The most obvious change for Lester in 2019 as a whole was that he used his cutter (34.2 percent, per Statcast) more than any other fastball, bumping the four-seamer (28.3 percent) down to second within his arsenal. The lefty has nearly doubled his cutter use since '16, and he has incorporated a changeup more in the past two years.

"Sometimes when you get out of sync," Cubs pitching coach Tommy Hottovy said in September, "it's because you're trying to do things that maybe aren't your strengths, over and over again, and you start creating bad habits. So a lot of times, you have to hit that reset button."

Looking forward

Lester will celebrate his 36th birthday this month. The lefty is not the overpowering ace that he was in his youth, but the Cubs firmly believe that he still possesses that thing that does not show up in the box score or the advanced data. He is determined to win and has a wealth of experience to lean on.

"We're not in the least bit writing him off," Epstein said. "We're not sort of like hoping he can hold his own. He's capable of being a really, really impactful pitcher for us."

Lester almost dares critics to think he can't still get the job done.

"I've been written off before," he said at the end of last season. "I think I've done all right for myself. I don't care about that. I care about winning. At the end of the day, you can say I'm done. That's fine. I want to win."

According to the Steamer projections, Lester is tabbed for 31 starts (a figure he has reached in each of the past 12 seasons) and a 4.73 ERA in 176 innings. The calculations show a slight dip in strikeout rate (20.5 percent in '20 compared to 21.6 percent in '19) and a tick up in walk rate (7.5 percent in '20 compared to 6.8 percent in '19).

Given Lester's change-can-be-bad declaration at the end of last season, it will be interesting to see how he alters the distribution of pitches in '20. En route to being the lefty's No. 1 pitch, his cutter has held relatively steady velocity-wise for the past three years (averaging 87.8 mph in '17, 88.1 in '18 and 87.9 mph in '19, per Statcast). At the same time, the four-seamer and sinker have both declined.

Lester's curveball (.239 wOBA and 40.3 percent whiff rate, per Statcast) was more effective than his changeup (.322 wOBA and 23.3 percent whiff rate) in '19, leading the lefty to rely more on the breaking ball in the second half. They key for Lester is finding consistency within his fastball mix to set up one of those two out pitches.

"I think he can still be really successful with the stuff that he has now," Epstein said. "He's doing a lot of different things now that he wasn't doing two or three years ago, but obviously as he advances in his career, there are adjustments that he has to make. And there's going to be challenges that come with it."