How should Nats evaluate McGowin's electric September?

Our offseason player review series continues today with Kyle McGowin, who emerged out of the blue this summer to be an at-times dominant reliever.

PLAYER REVIEW: KYLE McGOWIN

Age on opening day 2021: 29

How acquired: Traded with Austin Adams from Angels for Danny Espinosa, December 2016

MLB service time: 139 days

2020 salary: $563,500 (prorated $80,990)

Contract status: Under team control, arbitration-eligible in 2023, free agent in 2026

2020 stats: 1-0, 4.91 ERA, 9 G, 1 SV, 11 IP, 9 H, 6 R, 6 ER, 2 HR, 5 BB, 16 SO, 0 HBP, 1.273 WHIP, 96 ERA+, 4.01 FIP, 0.1 fWAR, 0.3 bWAR

Quotable: "The biggest thing, and I tell these kids: You have to create your own identity. You've got to know who you are, what kind of player you are. What kind of hitter you are, what kind of pitcher you are. McGowin went down there and figured that out. And he's doing well. But he did that. Nobody else could do that for us. He went down there and figured everything out, came back up here. He's very confident in what he's trying to do." - Manager Davey Martinez on McGowin

2020 analysis: After 12 inauspicious appearances the previous two seasons - two of those starts - McGowin entered this season well down the organizational depth chart. The Nationals didn't see much hope of him contributing as a starter, so upon reporting to the alternate training site in Fredericksburg they had him concentrate on relief, with an extra focus on mastering his best pitch: his slider.

It took more than a month and plenty of injuries to others, but McGowin finally got his promotion to D.C. on Sept. 2. And immediately impressed everyone who watched him. In his 2020 debut in Atlanta, he faced eight batters and retired seven of them, four via strikeout. His first four appearances all came against the Braves, and he held that vaunted lineup to one hit and two walks in total, striking out nine over 5 2/3 dominant innings.

Things did catch up to McGowin during the season's final week, though. Over his last three appearances (against the Phillies and Mets), he gave up six runs on seven hits, which ultimately skewed his final 2020 stats.

2021 outlook: The Nationals had no reason to believe McGowin would figure into their long-term plans when this season began. As it ended, they suddenly had reason to think he might actually have a place here in 2021 and beyond.

It's an incredibly small sample of work, so nobody's going to get too excited yet. But McGowin's slider is legit. Over his full big league career, opponents have hit only .134 and slugged .239 off that breaking ball. It can be a highly effective pitch, against batters from both sides of the plate.

In order to be successful over the long haul, McGowin is going to have to show he can at least use his fastball ball effectively to keep hitters off-balance and not let them sit on the slider. And he's going to have to prove he can hold up through the rigors of pitching in relief an entire season.

The Nats can't go into next spring assuming McGowin is going to be part of the mix. But they can certainly hope he is.