Through three starts, Lester—the offseason's big free-agent fish—has surrendered 12 runs and 24 hits in 15.2 innings. It's a small sample, and odds are the battle-tested left-hander will put up his usual solid numbers when all is said and done.
So far, though, Jake Arrieta is carrying the load in the City of Broad Shoulders.
It's not as if Arrieta came out of nowhere. Last season, the right-hander posted a 2.53 ERA and 0.989 WHIP, struck out 167 in 156.2 innings and finished ninth in National League Cy Young balloting.
Last July, Bleacher Report's Zachary D. Rymer called him "an ace-level pitcher who should be a rock in the Chicago Cubs' rotation for years to come."
Early in his career, though, few pegged Arrieta as a No. 1.
A fifth-round pick by the Baltimore Orioles in 2007, Arrieta made his big league debut in 2010. He showed flashes in parts of four seasons with the Orioles but never managed a sub-4.00 ERA, and the O's shipped him to Chicago in a 2013 deadline deal.
He's put it together on the North Side, possibly because of a workout regimen that has caught the attention of coaches and teammates.
"This guy should probably do the next Jane Fonda video on the male side of things," skipper Joe Maddon said, per WGNtv.com's Larry Hawley. "Put the leggings on."
"He's a freak," catcher Miguel Montero added, per Hawley. "He's working every day, and I'm like, 'C'mon, really?' That's Jake. He's a different cat for sure."
Or maybe it's the "half gallon of green liquid" he was spotted chugging before a game last summer, a kale juice concoction that's "a small but effective part of Arrieta's healthy routine," according to Mark Gonzales of the Chicago Tribune.
Whatever he's doing, it's working. Arrieta had another excellent outing Monday, allowing one run in seven innings with no walks and seven strikeouts in a 5-2 win over the Pittsburgh Pirates. He's now lasted into the seventh in all three of his starts and is averaging nearly a strikeout an inning.
Can he keep it up? The projection systems peg him for a good-but-not-great season, with ZiPS foretelling a 3.36 ERA with 159 strikeouts in 168 innings, per FanGraphs.
The Cubs would take it, particularly if Lester emerges as the ace they're paying him to be. Together, they could form a fearsome duo, as ESPN.com's Jesse Rogers pointed out:
The twosome should set the Cubs up nicely when they both pitch in a given series, but if we're talking postseason awards it's Arrieta who should have the better chance provided he can get to 200 innings. Durability is more important than great stuff, so right now Lester has the upper hand. But this could be the year Arrieta finally puts both of those aspects together. ...
... The Cy Young award will be a hotly contested race in 2015. The Cubs have two candidates. Watch out for the one making $16 million less than the other.
The key to Arrieta's success has been improved command. During last season's breakout campaign, he averaged 2.4 walks per nine innings, down from 4.9 in 2013. This season, that number has fallen to 1.7.
Arrieta has also been varying his pitches more since arriving in Chicago, relying less on his fastball and mixing in more off-speed stuff, as FanGraphs illustrates. In other words, he's maturing.
"Things will continue to change. I'll continue to evolve and develop over time," Arrieta told Hawley. "But I feel like the routine that I have in place is going to work for a while."
All statistics current as of April 21 and courtesy of MLB.com unless otherwise noted.