5 under-the-radar FA relievers with closer potential

There are still some proven closers out there on the free-agent market -- the Josh Hader, Jordan Hicks, Aroldis Chapman types. But a team might find the best value by signing a reliever who could become a closer if given the opportunity.

So let's find some of the pitchers who fit the bill. They might need to make some adjustments to take that next step, but with any luck, you might see these relievers collecting saves for their new teams in 2024.

Here are five free-agent relievers with closer potential. We'll see if they can reach it.

1) Robert Stephenson

Stephenson helped the Rays' bullpen go from worst to best down the stretch in 2023. The right-hander posted absurd strikeout rates after his trade to Tampa Bay from the Pirates in June -- with the Rays, Stephenson struck out 43% of the batters he faced, good for 14.1 K's per nine innings. The 30-year-old was terrific by all of Statcast's quality-of-contact metrics, too.

Stephenson's big adjustment was scrapping his slower, mid-80s slider for a harder, high-80s cutter that he was throwing nearly three quarters of the time by the end of the season. That sharper cutter, which generated a 60% swing-and-miss rate, played better with his fastball, which averaged a career-high 97 mph, and splitter, which at 89 mph is the same speed as his cutter, but has running action that mimics his four-seamer. That fastball-cutter-splitter trio gives Stephenson closer-caliber stuff.

2) Phil Maton

Maton has become a valuable part of the Astros' bullpen over the last three seasons as part of the bridge to closer Ryan Pressly. But he's been good enough that on another team without an established closer, he could earn some save opportunities himself.

Not only has the 30-year-old right-hander posted a 3.67 ERA in 162 relief appearances for Houston in the regular season, Maton has also allowed only one run in 18 postseason outings, all while averaging about 10 strikeouts per nine innings. He was particularly effective in 2023, combining high swing-and-miss, strikeout and chase rates with very low exit velocities and hard-hit rates allowed.

The key to Maton's success was his pair of breaking balls: a high-spin curveball that averaged an elite 3,156 rpm, and a "sweeper" slider that averaged 19 inches of horizontal break. Those two pitches accounted for nearly two thirds of Maton's total usage, and for the first time, his curveball, not his fastball, was his most-used pitch.

3) Shintaro Fujinami

Fujinami is one of the most interesting free-agent wild cards. He has one big hurdle to clear to become a shutdown reliever: his command, which was all over the place in his first season coming over from Japan in 2023. But if he learns how to command his stuff, that stuff is closer-level. You just don't find a pitcher who can throw 103 mph every day.

Fujinami notched 16 strikeouts last season on 100-plus mph fastballs, sixth-most of any pitcher in the Majors. The fastest of those was at 102.6 mph, a velocity only five pitchers reached on a K all year. That is top-of-the-scale velocity, and if you look on the free-agent market, Fujinami, Chapman and Hicks are basically the only places you can find it. With the Orioles, Fujinami showed flashes of being able to use that overpowering fastball to be a valuable late-inning reliever. The 29-year-old is a project, but a project that could pay off big for the right team.

4) Ryne Stanek

Here's another Astros reliever who could find closer work somewhere else. Unlike Maton, though, Stanek is a power pitcher. His 98 mph fastball comes first, and then he mixes in his high-80s secondary pitches, a splitter and slider that both generated whiff rates of 40% or higher in 2023.

Stanek has had some up-and-down results in Houston -- he had a 1.15 ERA in 2022 and four scoreless postseason outings on the Astros' World Series run, but a 4.09 ERA in 2023 and a rockier playoffs. All that being said, there's no question the 32-year-old has a big enough arm to be an overpowering relief ace, especially if he can figure out how to use that fastball-splitter-slider combo to put a few more hitters away.

5) Shelby Miller

Imagine Shelby Miller, closer. What a career revival that would be. Miller headlined our "unheralded free agent relievers that could make a difference" story last offseason, and he ended up doing just that for the Dodgers. Could the next step be a ninth-inning role?

Miller was terrific in 36 appearances for L.A. in 2023, posting a 1.71 ERA and striking out a batter per inning, and he also pitched a scoreless postseason outing in his first playoff action since 2014. Those numbers were for real, too. Miller held hitters to very poor contact -- his expected batting average allowed was just .188, 15th-best out of the 443 pitchers who faced at least 150 batters in 2023.

Miller brings high-quality stuff out of the bullpen. The 33-year-old righty generates plus movement on all three of his pitches: Miller's 94 mph fastball gets +2.4 inches of rise above average, his 86 mph splitter gets +2.5 inches of run above average, and his 82 mph slider gets +6.6 inches of horizontal break above average.