We know this much about Dave Dombrowski -- when he diagnoses a problem, he acts.

He made one of the most consequential moves of last season in late June, acquiring right-handed slugger Steve Pearce from the Blue Jays to address a deficiency against left-handed pitching. The acquisition barely merited mention outside of the transactions agate, but all Pearce went on to do was win World Series MVP.

June doesn't arrive until next week, but Dombrowski is already in fix-it mode. He typically gives his teams 40 games to sort out what's working and what isn't, and we passed that mark two weeks ago. With the Red Sox still trying to extricate themselves from a poor start — they're 5.5 games out of first place and a game and a half up on the Indians for the second wild card spot — a clear need has emerged in their bullpen.

The stats show the Red Sox with the most wins (15) and the sixth-lowest bullpen ERA in baseball (3.76), but don't let the numbers fool you. They are an arm short.

Matt Barnes could be an All-Star, Brandon Workman has been borderline unhittable, and veteran rookie Marcus Walden qualifies as a revelation, but they need help.

Ryan Brasier has not maintained last year's success, particularly against left-handed hitters. Heath Hembree has a propensity to allow home runs. Tyler Thornburg and Colten Brewer have been varying degrees of disastrous.

We've already argued that the next target should be a pitcher with closing experience, which would make the ninth inning less fraught after Barnes takes on the heart of the order in the seventh or eighth. But who will be out there? Here are three names.

Start with Sean Doolittle. The Nationals left-hander is a two-time All-Star, including last year, and has closed for parts of four seasons. He was having a tremendous season until imploding in his last outing and allowing four runs while doubling his ERA in a loss to the Mets. He's still 3-1 with a 3.43 ERA and 25 strikeouts in 21 innings.

The Nationals are once again grossly underachieving — only a game and a half ahead of the Marlins, who aren't even trying — and it's a foregone conclusion that they will be sellers come July. The 32-year-old Doolittle represents a prime trade asset. He's making $6 million this year and has a $6.5 million team option for 2020.

He'd solve two problems for the Red Sox, being able to close and also providing a left-handed power arm. He lives almost exclusively on a 93-95 mph four-seam fastball, and he's experienced. Add a quirky personality — he has made it his mission to patronize an independent bookstore in every road city, and he hosted Syrian refugees for Thanksgiving — and he'd liven up the Red Sox clubhouse.