The Cubs, in dire straits with a banged-up pitching staff, made an intriguing addition via trade Thursday by acquiring left-handed pitcher David Peterson from the Mets for Minor League prospect Cole Mathis.
You should hardly expect flashy trades at this point in the season, and Peterson is not that. He’s carrying a 6.09 ERA across 16 appearances, and he lost his spot in the rotation because of his struggles. The 30-year-old will also be a free agent at the end of the season.
But this is the type of deal that is available near the end of June, and it’s the type of deal the Cubs felt they had to make with five starters on the injured list. In better news for the North Siders, there’s some reason to believe Peterson can make marked improvement with the change of scenery -- which, ironically, is nothing more than a change in dugouts at Citi Field on Thursday.
We’ll hone in on three keys for Peterson’s fit in Chicago, the first of which should be fresh in the minds of Cubs and Mets fans alike.
Ground-ball machine
Even as Peterson has faltered in 2026, he still owns a 52.9% ground-ball rate, ranking in the 89th percentile among qualified pitchers. That’s on par for Peterson, a sinker-slider type who has induced ground balls at 52.3% across his seven-year career.
The Mets, however, have been among MLB’s worst defenses in 2026, worth -4 Fielding Runs (19th) and -10 Outs Above Average (21st). Those numbers get even worse when you filter for just New York’s infielders, ranking 26th in FRV (-11) and 24th in OAA (-11). A six-error performance in the nightcap of Wednesday’s double-header against the Cubs certainly didn’t help.
On the other hand, the Cubs boast MLB’s best defense and best infield by those same metrics. They have 33 FRV as a team thus far, 10 more than the second-place Padres’ 23. Their 38 OAA also comfortably clears the second-place Dodgers’ 23. Meanwhile, the infield is first with 22 OAA and tied for first (Cardinals) with 19 FRV.
There’s a reason the Chicago defense is littered with Gold Gloves. Infielders Alex Bregman, Dansby Swanson and Nico Hoerner all own at least one, while first baseman Michael Busch is tied for this season’s lead at his position in both FRV (5) and OAA (6). Outfielders Ian Happ and Pete Crow-Armstrong have both been Golden, too.
Thirty-three of Peterson’s 82 hits allowed this season (40.2%) have come on the ground. There’s a good chance that number could plummet when he suits up for the Cubs.
Righting the (FIP) ship
Peterson’s expected ERA (4.83) doesn’t inspire much confidence, and he’s been 4.58 or higher in that metric since 2023. Allowing too much hard contact, as the southpaw has, will lead to that inflated number.
But Peterson does have a better-looking 3.85 FIP, a metric that focuses on the things a pitcher has the most control over: strikeouts, walks, hit by pitches and home runs. In fact, Peterson’s FIP has been in the mid-threes in each of the past three seasons.
That gives further confidence that a defense as good as Chicago’s can help Peterson find better results.
Pitch shape
Peterson has never been a hard thrower, with his highest average four-seam velocity coming in 2022 at 93.7 mph. He’s sitting 92.3 mph on the heater this year (92.1 on his sinker), putting him in the bottom 20th percentile of qualified pitchers.
The Cubs, too, have been somewhat infamous for deploying softer-tossing starters in recent years. But Peterson has a unique shape on his fastball that Chicago has found success with in the past, and perhaps that’s another reason why Jed Hoyer and Co. targeted Peterson.
In a day and age when many are seeking more rise and tail on the fastball, he induces more of a cutting action. The pitch gets just 2.6 inches of arm-side break this season, 5.4 inches less than the average left-handed four-seam fastball.
Cubs talented lefty Justin Steele (currently on the 60-day IL) has never generated more than 2 inches of arm-side tail. Another under-the-radar acquisition by the Cubs, Drew Pomeranz, averaged 1.2 inches of arm-side break in 2025. Pomeranz, subsequently, turned in an excellent season out of the bullpen.
The Cubs likely see something in Peterson that they can work with. After all, his peak performance is still there somewhere. He was an All-Star selection in 2025, carrying a sub-3.00 ERA entering his Aug. 13 start against the Braves.
Peterson allowed six earned runs that day, and things have gone downhill since. But there may be better days ahead, and he’ll have a chance to quickly win over the Cubs faithful, assuming he can eat some innings for a depleted rotation.