The New York Mets and pitching coach Jeremy Hefner are parting ways. The Mets originally brought in the former Mets starting pitcher as a coach during the 2019-2020 offseason. However, he has definitely been a mixed bag, to say the least. There have been plenty of pitchers the Mets have seen get worse while under Hefner’s tutelage, but these three falling off a cliff were some of the most shocking.

1) Ryan Helsley

The Mets acquired Ryan Helsley from the St. Louis Cardinals at the 2025 deadline with the hopes that he could be a shutdown setup man for Edwin Diaz. It wasn’t an unreasonable hope either. Helsley was one of the best closers in baseball from his 2022 breakout up until the Mets traded for him. He had a 1.90 ERA, 2.36 FIP, and 1.03 WHIP over 203.2 innings of work, ranking in the top three among all qualified relievers in the first two stats.

Helsley also had some outstanding peripherals. He struck out nearly a third of opponents with a 32.9% K%. With a 9.2% BB%, he was one of only 11 qualified bullpen arms with a K% over 30% and a BB% under 10%. Home runs were not much of an issue either, with a 0.62 HR/9 ratio and a barrel rate clocking in at just 5.8%.

However, Helsley was one of the worst relievers in baseball after the Mets acquired him. He managed a 7.20 ERA, 5.19 FIP, and 1.80 WHIP over 21 innings in New York. He ranked in the bottom ten among all RPs in ERA and WHIP. Helsley was never as good as Greg Maddux when it came to command, but he couldn’t find the zone with the Mets. The hard-throwing reliever allowed 11.6% of opponents to reach via free pass. He wasn’t getting batters to swing and miss either, with a 23% K%. When they made contact, it was usually hard contact, with a 1.80 HR/9 and 8.1% barrel rate. He blew four saves, and his -1.90 win percentage added was the second lowest among RP’s after the trade, making him a primary culprit for the Mets’ late-season collapse.

The only saving grace is that Helsley was only a rental and is now a free agent. The Mets and Jeremy Hefner never seemed to be able to get Helsley back on track. This is despite the fact that Helsley had a 125 FanGraphs Stuff+, nearly identical to the 126 mark he had with the Cardinals from 2022-2025. If Hefner couldn’t help a pitcher with that good of stuff straighten things out, then he may not be the man for the job.