The Red Sox have made it clear during the offseason that strengthening the starting rotation is their top priority for this winter, but according to Chris Cotillo of MassLive, Boston is still searching for rotation arms, even outside of their rumored pursuit of outfielder Teoscar Hernandez. The Red Sox are also reportedly interested in infielder Amed Rosario and right-handed reliever Robert Stephenson, though Cotillo adds a caveat that it’s unclear how serious the team is about either player.
In Queens and Cleveland from 2019 to 22 (after being included in the return package for Franciscor Lindor), Rosario, 28, made his big league debut for the Mets in 2017. He was essentially a league average starter at shortstop, slashing.282/.315/.412 while playing defense that varied from above average to well below average year to year. Rosario had a bit of a poor year in 2023, hitting just.265/.306/.369 in 92 games for the Guardians despite playing excellent defense. He was traded to the Dodgers in the middle of the season, where he got much less playing time. Rosario had the poorest season of his career overall, finishing with a wRC+ of 88 and just 0.2 fWAR. On MLBTR’s annual Top 50 MLB free agents list, Rosario came in at number 39. Our projection for him was a two-year, $18MM contract.
Rosario has a lot of shortcomings, but he would still make sense as an addition to a Boston team that saw the keystone produce the second-worst output in the majors the previous season. In fact, Rosario’s slash line from last season—which was his first taste of a big league role—would have been a significant improvement over the Red Sox second baseman’s 2023 line of.240/.286/.376. Rosario also played well defensively at second base in 36 games with the Dodgers last season. The Red Sox would strengthen their depth at a position of obvious need by adding Rosario, even though he might not be the most significant free agent on the market. Moreover, doing so wouldn’t prevent the team’s best infield prospects, Marcelo Mayer and Nick Yorke, from making their way into the major leagues later in the season.
Conversely, Stephenson is coming off a much better platform season. The Reds selected the 30-year-old right-hander in the first round of the 2011 draft, and he made his major league debut as a starter in 2016. Before deciding to go full-time to the bullpen in 2019, where he experienced greater success, Stephenson battled miserably in the role for portions of three seasons in the majors. After only pitching ten innings in the abbreviated 2020 season, the right-hander had a 3.76 ERA (125 ERA+) and a 3.63 FIP in his debut season as a full-time reliever. He was then transferred to Colorado in exchange for Jeff Hoffman. Stephenson’s first season with the Rockies was incredibly successful; the right-hander recorded an identical 3.63 ERA to his 2019 performance, with an ERA of 3.13.
After having a difficult season in 2022, where he split time with the Rockies and Pirates, Stephenson began 2023 poorly for Pittsburgh, giving up nine runs (eight earned) in just fourteen innings. When June rolled along and the Pirates traded Stephenson to the Rays, where he would play his most productive stretch of his career, his luck immediately changed around. Stephenson struck out an amazing 42.9% of hitters he faced while walking just 5.7% after switching up his pitch mix to include a cutter instead of a slider as his main breaking ball. The righty’s elite run prevention stats are equally striking; in 38 1/3 innings pitched for the Rays this season, he recorded a 2.35 ERA and 2.45 FIP. Thanks to his prolific output, MLBTR ranked Stephenson as the 27th greatest free agent of the offseason, projecting a four-year, $36MM contract.
Nevertheless, there isn’t exactly the same fit between Rosario and Boston as there is with Stephenson. In addition to veteran right-handers Kenley Jansen and Chris Martin leading a formidable bullpen, the Red Sox also had successful seasons from Josh Winckowski and John Schreiber in 2023. Given the strong combination of righties in the team’s bullpen, it doesn’t appear probable that the Red Sox will be able to outbid teams in need of a bullpen, like the Rangers, Astros, Cardinals, and Cubs, for Stephenson’s services. Nevertheless, Cotillo speculates that the Red Sox might use the signing of Stephenson as a way to take advantage of their strong bullpen and arrange a trade for Jansen, Martin, or Schreiber. In theory, a team with starting pitching depth, like the Astros or Marlins, who probably has to strengthen other aspects of the roster, may find it alluring to package a top relief arm like Jansen or Martin with a young outfielder like Wilyer Abreu or Jarren Duran.