Closer Craig Kimbrel is one of the top players remaining on the free agent market. (Steven Senne/Associated Press)

WEST PALM BEACH, Fla. — Once Bryce Harper signed with the Philadelphia Phillies last week, it seemed the National League arms race may have finally reached its conclusion.

Not so fast.

A person familiar with the Washington Nationals’ plans said the team remains interested in signing star closer Craig Kimbrel, confirming multiple reports that have linked the free agent with one of the league’s most active spenders. Kimbrel, 30, is a seven-time all-star who recorded six saves last postseason for the World Series-winning Boston Red Sox.

Signing him makes sense for the Nationals, at least on the surface, with their bullpen a potential question mark despite the additions of Trevor Rosenthal and Kyle Barraclough. But it could also make sense for two of their NL East rivals; reports indicate the Phillies and Atlanta Braves are in the mix, too.

If the Phillies get Kimbrel, it would cap an offseason shopping spree that included landing Harper on a 13-year, $330 million deal, trading for star catcher J.T. Realmuto, trading for shortstop Jean Segura, signing reliever David Robertson and bringing in outfielder Andrew McCutchen. The Braves, for whom Kimbrel pitched from 2010 to 2014, could use bullpen help after adding third baseman Josh Donaldson to an already-loaded lineup.

The Nationals have positioned themselves for a tight division race that should include the Phillies, Braves and New York Mets, who added power and relief pitching this winter. Washington moved on from Harper by signing left-handed starter Patrick Corbin to a six-year, $140 million contract; adding veteran catchers Yan Gomes and Kurt Suzuki; inking second baseman Brian Dozier to a one-year deal; signing right-hander Anibal Sanchez for two years; bringing back power-hitting first baseman Matt Adams; bringing back starter Jeremy Hellickson; and building their bullpen with Rosenthal and Barraclough.

So maybe it’s not a surprise that Kimbrel, one of the last-standing dominoes in a slow offseason, could land in a division full of spending competitors. And if he does, his destination could determine the favorite heading into the season.

Adding Kimbrel would certainly help the Nationals from a competitive standpoint. The financial implications, however, are much trickier. But of the reasons Kimbrel is a good fit for the Nationals, none is stronger than this: Their bullpen is top-heavy — with all-star closer Sean Doolittle and Rosenthal highlighting a group of not-as-proven arms — and they have said, over and over this spring, that they don’t want to overtax those two.

“Like I’ve said, my biggest concern is keeping these guys healthy,” Nationals Manager Dave Martinez said Sunday morning of his bullpen. “You’ve got Trevor come off of Tommy John. Barraclough had injuries last year. Doolittle missed three months with a toe injury. Keeping all these guys healthy is the key. If we can stay healthy, our bullpen’s going to be really good.”

What better way to keep your top options healthy than by adding another reliable arm to the mix? Kimbrel is way more than that, maybe the best closer of this generation, the kind of pitcher who can change a team even though he throws, at most, one inning per night. He could close, give Doolittle nights off, pitch the eighth inning when needed, match up with top hitters in big situations and so on.

If he joined the Nationals, they would have a lethal late-inning combination of Kimbrel, Doolittle and Rosenthal. Kimbrel is a right-hander who had a 2.73 ERA and 42 saves last season. Doolittle is a lefty who, despite missing two months with that toe injury, had a 1.60 ERA in 45 innings. Rosenthal may have missed all of last year recovering from Tommy John surgery, but he is a former all-star closer who already hit 100 mph again this spring. That trio would complement a starting staff of Max Scherzer, Stephen Strasburg, Corbin, Sanchez and Hellickson, which will cost the Nationals around $96 million this year and is the core of their identity.

Signing Kimbrel would also bump the team’s secondary relievers into lesser roles and only strengthen the bullpen, putting Barraclough, Matt Grace, Wander Suero, Sammy Solis, Justin Miller and Koda Glover in fewer high-leverage situations.

But all that logic could fall to the most important variable of all: money. There is no salary cap in baseball, but the Nationals have pledged to stay under the competitive balance tax threshold for the first time since 2016. The threshold for this season is $206 million. If they went over for a third year in a row, they would be taxed 50 percent for every dollar spent above the threshold. Cot’s Baseball Contracts projects the Nationals at around $10 million below the threshold, while factoring in potential performance incentives; internal calculations have the team a bit further from the line. Either way, a move for Kimbrel would likely push them over.

What the market for Kimbrel is, exactly, is hard to measure. He entered the offseason looking for a six-year, nine-figure deal. He will not get that. He is more likely to get a short-term deal with a high average annual value, according to one person familiar with his negotiations, maybe in the $15 million to $20 million range.

Let’s say, for the fun of it, that he demands $18 million per year and Washington is $10 million below the CBT threshold. That means, if Kimbrel was the Nationals’ only other addition, they would pay around $4 million in overages. Minor acquisitions in the coming months could boost that fee by $1 million or so. That feels like a worthy investment when four teams believe they can win the NL East — and one of them just signed the Nationals’ homegrown superstar to the largest contract in the history of North American sports.

Yet if Washington is serious about staying away from the CBT, Kimbrel would seem to be off the table. That would give both the Phillies and Braves a better chance to get him instead. And that could be an even bigger price to pay.

Read more on the Nationals:

Analysis: Does the Nationals’ best lineup have Trea Turner leading off?

Svrluga: The Nationals don’t do business the way most MLB clubs do. Just ask Bryce Harper.

For baseball prospects, a lower jersey number is a positive sign for their career

‘There was a big number’: Trevor Rosenthal impresses right away for Nationals

Nationals are building up starter Joe Ross’s workload

Dave Martinez, in second spring training, shows growth in shifted approach