Red Sox pitching prospect Ryan Zeferjahn (0.00 ERA in April) off to strong start for Double-A Portland

Following Tuesday’s performance, Zeferjahn is now 1-0 with a 0.00 ERA (0.57 FIP) and 19 strikeouts to two walks over six relief appearances (11 2/3 innings) for Portland this season. He has converted both of his save opportunities while holding opposing hitters to a .178 batting average against.

Among 99 pitchers in the Eastern League who entered Wednesday with at least 10 innings under their belts to this point in the year, Zeferjahn ranks third in strikeouts per nine innings (14.66), sixth in walks per nine innings (1.54), second in strikeout rate (40.4 percent), seventh in walk rate (4.3 percent), 22nd in batting average against, 11th in WHIP (0.86), 27th in swinging-strike rate (14.3 percent), first in ERA, second in FIP, and second in xFIP (1.55), per FanGraphs.

Zeferjahn is in the midst of his fourth full professional season after originally being selected by the Red Sox in the third round of the 2019 amateur draft out of the University of Kansas. The former Jayhawak signed with Boston for $500,000 and made his pro debut as a starter but has since transitioned to the bullpen on a full-time basis.

Though he struggled to a 5.02 ERA (5.44 FIP) in 34 outings (43 innings) for Portland in 2023, Zeferjahn has been turning heads with improved results so far this year. As noted by The Boston Herald’s Mac Cerullo, Zeferjahn was recently singled out by a Red Sox front office source “as someone who has raised eyebrows” thanks in part to a great offseason.

“The focus for him was throwing strikes, being competitive in the zone,” Brian Abraham, Boston’s director of player development, said of Zeferjahn. “It’s only been a short amount of time this year but he’s done that.”

Zeferjahn, who just turned 26 in February, is currently regarded by SoxProspects.com as the No. 46 prospect in the Red Sox’ farm system, which ranks 21st among pitchers in the organization. The 6-foot-5, 209-pound righty operates with a four-pitch mix that consists of a high-90s fastball that can touch triple digits, a high-80s slider, a low-80s changeup, and a high-70s curveball.

Considering the fact that he can once again become eligible for the Rule 5 Draft at the end of the year, it would not be too surprising if Zeferjahn made the jump from Portland to Triple-A Worcester before long. A promotion to Worcester may help the Red Sox in determining if Zeferjahn is worthy of a spot on the 40-man roster this winter.