Doolittle seized closer's role and now expects to keep it long-term

As we transition into offseason mode here, we're reviewing each significant player on the Nationals roster. We continue today with Sean Doolittle, who was acquired in July to help fix the Nats bullpen and wound up excelling as closer.

PLAYER REVIEW: SEAN DOOLITTLE

Age on opening day 2018: 31

How acquired: Traded from Athletics with Ryan Madson for Blake Treinen, Jesus Luzardo and Sheldon Neuse

MLB service time: 5 years, 122 days

2017 salary: $2.63 million

Contract status: Signed for $4.38 million in 2018, $6 million club option (or $500,000 buyout) for 2019, $6.5 million club option (or $500,000 buyout) for 2020 (option becomes mutual if Doolittle finishes 100 games between 2018-19).

2017 stats: 2-0, 2.81 ERA, 53 G, 24 SV, 51 1/3 IP, 34 H, 18 R, 16 ER, 5 HR, 10 BB, 62 SO, 0 HBP, 0.857 WHIP, 1.7 WAR

Quotable: "He's got one of the best, if not the best, fastballs in the game that I've seen, since Billy Wagner." - Madson on Doolittle

2017 analysis: The Nationals entered the summer desperate for relief help, and not just one reliever. Mike Rizzo wound up killing two birds with one stone in one impressive mid-July trade, acquiring both Doolittle and Madson from the A's for Treinen and two minor leaguers.

At the time, the Nats didn't know for sure what role Doolittle would hold, but it quickly became clear he was their best option to close. Though he had only minimal ninth-inning experience, the left-hander thrived under pressure and was equally effective against hitters from each side of the plate.

Doolittle's success is particularly remarkable considering he throws more than 90 percent fastballs. He commands that pitch exceptionally well, though, and gets late movement on it to induce swings and misses.

2018 outlook: The Nationals acquired Doolittle not only to help address their bullpen this year but for years to come. He's under club control through 2020, so he's here to stay and should anchor this relief corps for quite some time.

Which isn't to say there aren't a few concerns. For starters, Doolittle has a lengthy history of injury, especially his shoulder. Dusty Baker and Mike Maddux did a good job managing his workload this season, making a point to use him on back-to-back days as infrequently as possible. Dave Martinez and his new pitching coach will need to come up with a plan that works to keep Doolittle on the active roster the entire season.

Doolittle's arsenal, meanwhile, does tend to become awfully predictable. If he can continue to locate with pinpoint precision, he can probably continue to get away with it. But he has said he'd like to incorporate more of his off-speed stuff in the future, so look for him to try his slider and changeup with some more regularity next spring in attempt to diversify his repertoire.