Evaluating the ups and downs of Zach Pop’s rookie year.
Coming off Tommy John surgery and lacking substantial high-minors experience, Zach Pop was challenged with making the leap to Major League Baseball. He handled it solidly and flashed the potential to stick as an impactful reliever for the foreseeable future.
- April 3: made MLB debut vs. Rays
- June 3: Tyler Jones sent from Marlins to Diamondbacks as PTBNL to complete Pop trade
- June 30: earned first career win
- August 14: placed on 10-day injured list (right middle finger soreness)
- August 24: sent on rehab assignment
- August 31: activated from 10-day injured list
By The Numbers
The Marlins acquired Pop via the D-backs immediately after he had been plucked from the Orioles in the Rule 5 draft. He entered spring training with the inside track at an Opening Day roster spot—players in his situation cannot be directly optioned to the minor leagues. The Canadian right-hander secured a job in the bullpen with five effective Grapefruit League outings (zero earned runs allowed).
Pop’s 67.7% fastball usage is high by modern MLB standards. He possesses above-average velocity on it (averaged 95.4 miles per hour). Moreover, his sinker ranks in the 94th percentile in horizontal break and the 81st percentile in vertical break compared to other MLB fastballs, according to Quality of Pitch. He’s especially fond of throwing heaters to the arm side and frequently used them to induce ground balls (average launch angle of negative two degrees).
Pop stumbled early on, entering April 17 with a 18.90 earned run average (7 ER in 3.1 IP). But from that point through season’s end—a span of 46 appearances—he allowed only one home run. After the All-Star Game, he kept everybody inside the yard, joining an exclusive club of eight major leaguers to pitch a homerless second half (min. 20 IP).
I feel like this went under the radar: Pop changed his slider coming out of the All-Star break. The pitch’s velocity skyrocketed! All 62 of his highest slider velos this season were recorded on or after July 16, according to Baseball Savant. Meanwhile, his fastball velo was relatively steady.
Perhaps he altered the pitch’s design in response to MLB’s crackdown on foreign substances? Unable to spin the ball as efficiently, he conceded vertical break to focus on velo.
Getting first-pitch strikes was crucial for Pop. He limited batters to an impotent .147/.198/.179 slash line in 102 plate appearances when he got ahead 0-1. It’s fun to dream about what he can accomplish if he’s able to do that more consistently. His first-pitch strike rate was just 51.6% of the time, a far cry from the MLB average of 60.5%.
As the season progressed, the Marlins began to trust Pop with inherited baserunners. There’s still a lot of room for him to improve in that department. Although he only allowed seven of his own runs (five earned) after the All-Star break, 11 of the 17 runners he inherited came around to score.
Zach Pop, Absurd Fastball Movement.
— Rob Friedman (@PitchingNinja) March 16, 2021
Did you stay up late to watch Zach Pop? You should’ve stayed up late to watch Zach Pop.
First time working multiple innings as a major leaguer and he handled it perfectly. pic.twitter.com/D01yxie0CI
— Fish Stripes (@fishstripes) April 23, 2021
Will Zach Pop Be Back?
Nearly every young Marlins pitcher is potentially on the table in offseason trade negotiations. After satisfying his Rule 5 conditions in 2021, Pop still has all three of his minor league options intact, which will only augment his value to other teams.
That being said, we should operate under the assumption that Pop will report to Marlins spring training and compete for a role in middle relief. The fallback plan? Sending him down to Triple-A and getting him reps in high-leverage situations so that he’ll be prepared for everything once there’s room for him in Miami.