Jeremy Hellickson, seen here last season as a member of the Orioles, has a career 4.12 ERA and won the AL rookie of the year award in 2011 as a member of Tampa Bay, where Dave Martinez was bench coach. (Scott R. Galvin/USA Today Sports)

WEST PALM BEACH, Fla. — The Washington Nationals entered spring training with a nearly complete roster, with few spring training competitions to monitor or spots up for grabs. The role of fifth starter lingered as one of the few uncertainties, with homegrown right-hander A.J. Cole and top pitching prospect Erick Fedde standing as promising candidates, but no sure things.

On Friday, the Nationals brought in a surer thing to fill that spot when they agreed to a minor league deal with right-hander Jeremy Hellickson, according to a person familiar with the situation. Hellickson will be in camp on a nonroster invitation and could need time to pitch his way into regular season shape. But the 30-year-old is a season removed from earning a qualifying offer from the Phillies, and he is a proven back-end starter who always gives the Nationals fits. If he is healthy, and when he is ready, Hellickson could solidify the back end of that rotation at an undisclosed, likely bargain price.

Hellickson struggled last season, one he split between Philadelphia and Baltimore while pitching to a 5.43 ERA. He owns a 4.12 career ERA and a 69-69 career record, and he has never been known as a guy with blow-you-away stuff. But he is consistent and reliable, with plenty of experience in the National League East, and plenty of history with Nationals Manager Dave Martinez. Hellickson won the 2011 American League Rookie of the Year Award while playing for Tampa Bay while Martinez was the bench coach there.

Cole’s numbers are not drastically different than Hellickson’s. Since the start of the 2016 season, Hellickson has made 62 starts in which he has pitched to a 4.51 ERA. Cole has made 19 appearances and 16 starts in which he has pitched to a 4.38 ERA. Given those numbers, and that Hellickson has yet to prove himself this spring, the competition is not over simply because of his presence. But the acquisition reveals the Nationals’ desire to bolster their big league starting pitching depth, which extends to Tommy Milone and Edwin Jackson after Cole and Fedde but drops off from there.

Scott Boras represents Hellickson, meaning after rumors of talks with Jake Arrieta, the Nationals got a starter represented by Boras after all. Should Hellickson secure the fifth spot in the rotation, four of the Nationals’ five starters will be Boras clients. Three of their eight projected Opening Day starters are Boras clients, too.

Whomever represents them, the Nationals’ starters are proven and durable — but they are not young. At 29, Stephen Strasburg is the youngest of the big four. When Gio Gonzalez stretched a bit on the mound during his start Friday, Martinez hurried out to check on him in a panic. Gonzalez just laughed and said he was fine. But should one of the four succumb to injury, the Nationals do not have the depth to withstand further trouble.

If Hellickson looks more like the pitcher that baffled the Nationals and the rest of the league in 2016 — when he was 12-10 with a 3.71 ERA and 1.15 walks plus hits per inning pitched in Philadelphia — that depth has improved dramatically. If not, the Nationals have not paid much to see what he has. For now, he looks like a legitimate candidate to serve as their fifth starter, though given that he has yet to pitch this spring, no one will hand that job over quite yet.

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