Red Sox pitching prospect Jay Groome has struck out 19 of the first 39 batters he has faced since promotion to Double-A Portland

Groome, who turned 23 in late August, initially began the 2021 minor-league season at High-A Greenville, where he posted a 5.29 ERA and 4.00 xFIP over 18 starts (81 2/3 innings pitched) before earning a promotion to Portland earlier this month.

In his Sea Dogs debut, which came against the New Hampshire Fisher Cats, Groome fanned a season-high 10 batters while walking none over five solid, scoreless innings of work.

While he had to wait more than a week to make his next start for the Sea Dogs, the 23-year-old southpaw was yet again impressive on Sunday. In picking up nine strikeouts in his latest outing, Groome has now fanned 19 of the first 39 hitters he faced at the Double-A level.

It’s a small sample size, of course, but among Double-A Northeast pitchers who have thrown at least 11 innings this season, Groome ranks second among them in strikeout percentage (48.7%), third in walk percentage (2.6%), and third in xFIP (1.89), per FanGraphs.

The Red Sox originally selected Groome with the 12th overall pick in the 2016 amateur draft out of Barnegat High School in New Jersey. He underwent Tommy John surgery in the spring of 2018 and was added to Boston’s 40-man roster last November in order to receive protection from the Rule 5 Draft.

Listed at 6-foot-6 and 251 pounds, Groome is currently regarded by Baseball America as the No. 9 prospect in Boston’s farm system, which ranks fourth among pitchers in the organization.

Having to undergo Tommy John surgery forced Groome to become a different pitcher, but his ceiling is still relatively high.

Per his Baseball America scouting report, the lefty “has the raw materials of a left-handed starter, including a powerful build, a controlled, repeatable delivery and giant hands that allow him to manipulate the ball.”

Additionally, Groome operates with a four-pitch mix that consists of a 92-95 mph fastball that “has missed a ton of bats” this year, a curveball that “has been more of an average pitch” post-Tommy John, a recently-added slider, and a changeup.

According to MassLive.com’s Christopher Smith, “there’s a belief in the Red Sox organization [that Groome’s] slider has become his best secondary pitch, especially to left-handed hitters.”