Guardians shaping prospect Rosario at the plate, on the bases
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CINCINNATI — In the third inning of the Guardians’ Spring Breakout game against the Mariners on March 14, Alfonsin Rosario lashed a first-pitch sinker from Mariners prospect Logan Evans into left-center field for a double. That hit had a 106.8 mph exit velocity.
Spring Breakout offered Guardians fans a sampling of Rosario (Cleveland’s No. 25 prospect), a toolsy outfielder with an impressive blend of power and athleticism in the field and on the basepaths. The 20-year-old has 55-grade power, 60-grade speed and a 70-grade arm (on a 20-80 scouting scale), according to Pipeline.
The Guardians acquired Rosario from the Cubs on Nov. 20 for reliever Eli Morgan.
“The power and the tools stood out to us,” Guardians VP of player development Stephen Osterer said. “The profile is pretty loud when he hits the ball, and the tools in the outfield to potentially play an above average outfield [stand out]. A lot of room to grow to get to that point, but there were some raw tools.
“He’s young for [High-A] this year. We were just excited to get that type of skillset and tool set into the system and help refine and develop [him] over time.”
Chicago selected Rosario in the sixth round of the 2023 Draft, and he slashed .230/.344/.423 with 16 homers and 20 stolen bases in 109 games in Single-A last year, in his first full season of pro ball. That production has translated to High-A Lake County this season. Through 25 games, Rosario had a .276/.330/.490 slash line with six doubles, five homers, 18 RBIs and five stolen bases.
Rosario has worked on getting his bat path in the zone more consistently and his overall timing down since joining Cleveland. The early returns have been encouraging. Entering Saturday, his strikeout rate was 23.6 percent, down from 32.2 percent in 2024. His contact rate was 69.9 percent, up from 59.3 percent in ‘24.
“The profile is very much loud and hard contact and power and pop, with some of the K rates probably being higher than he or others would liked to have seen last year,” Osterer said. “… We’re really just trying to get the bat path to create better zone coverage overall to kind of pull back those K rates — which he’s shown a really good job of doing.
“It’s shown up in better damage and better [two-strike] count production. He’s done a lot of work to move the needle on those things, and we’re seeing with the K rates dropped significantly so far, and the power is shining through as it has in the past — and maybe to a bit of a higher degree as well.”
Alongside the power is Rosario’s skill running the bases. He has good speed, but the Guardians have worked with him and other prospects on the components to be a quality baserunner, from preparing for pitchers to their reaction time on the field and leadoff lengths.
“There’s a lot of room for growth there to get even more bags, because when he does get moving, he is pretty quick,” Osterer said. “So it’s some of the nuance and the refinement of what it takes to actually be a bag stealer at the big league level, and there’s a lot of things that go into that, not just being fast. So he’s learning some of those things.
“He loves these things and is bought in. … Probably expecting him to get more [stolen bases] than he did last year.”
Rosario has a few more years of development ahead of him on the pathway to the Majors. For the Guardians, right now it’s about working toward what his performance could be like, with the tools in his bag, when he is ready for the big leagues.
“It’s trying to have a vision for what the long-term version of Rosario could be,” Osterer said. “And also acknowledge that he has a vision of himself as a player and try to meet in the middle and work towards that, knowing that those things could change in the medium to longer terms as well.”