Lester is locked in during his starts, rarely breaking from a determined look. You won't find him smiling on days he pitches, as that's just part of his approach.
"My mom gets on me about that," Lester said on the Bernstein & McKnight Show on Wednesday. "My fifth day is my day. That's my day, and that's my opportunity to help the team. The other four days days when I'm in the dugout, I'm doing nothing to help the team. I have no impact on the outcome on that game. So, when I get my turn, I want my turn to go well and I want to win that game.
"When I'm out there, I want my day to go well so bad. That's what drives me. I love to compete. I love the cat-and-mouse game of pitching, of, 'I have a better plan than you do today.' I have to go out there and execute it. And then when I don't execute it, it's frustrating because I have to wait four more days to go out there and do it again."
Lester posted a 4.46 ERA over 31 starts in 2019. Signed to a six-year, $155-million deal with the Cubs in December 2014, he's entering the final season of his contract.
Now 36, Lester has built a successful 14-year career in large part because of his drive to be great each fifth day. After strong outings, he refuses to get himself too high. On the flip side, Lester also isn't afraid to rewatch a poor performance the night of an ugly game.
"I'm more likely to beat myself up than pat myself on the back," he said.