Brandon Walter entered the 2021 minor league season in anonymity. Nothing on his résumé suggested the emergence of a top pitching prospect in the Red Sox system.
The Red Sox had taken him out of the University of Delaware after his redshirt junior season in the 26th round of the 2019 draft. He was one year removed from Tommy John surgery and mostly throwing in the mid- to high-80s.
Once Walter signed with the Sox for $35,000, the team didn’t assign him to Lowell — the more advanced of its short-season affiliates. Instead, he stayed in Fort Myers to work as a starter in the rookie level Gulf Coast League. Then, with the minor league season canceled in 2020, Walter wasn’t among the roughly 60 minor leaguers invited to the Sox’ instructional league program that fall.
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Yet entering 2021, none of that discouraged Walter. To the contrary, he was brimming with anticipation as he prepared for spring training.
“It was kind of like I had this secret. I couldn’t wait to show everybody,” said Walter. “I treated it as if the people watching me had never seen me before in this way. I wanted to kind of open eyes.”
Walter did just that, forging a 2.92 ERA in 89⅓ innings between Low-A Salem and High-A Greenville while ranking in the top 10 in the minors among pitchers who threw at least 80 innings in strikeout rate (36.3 percent) and strikeout-to-walk ratio. Opponents hit .199 against him.
“He absolutely dominated,” said Salem pitching coach Nick Green.
Walter now ranks among the top handful of pitching prospects in the Red Sox system. A number of teams have asked about him in trade talks.
So where did he come from, how did he end up in the Red Sox system, and how did he make his leap forward in 2021?
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Delaware isn’t exactly a hotbed of amateur baseball talent. Just three players this century who have been drafted out of high schools or colleges from the First State have reached the big leagues.
But entering 2019, Reed Gragnani — the Red Sox’ mid-Atlantic scout in 2018-19 — knew he’d want to make a trip thanks to a trusted source.
Gragnani roomed in college at the University of Virginia with Rob Amaro, the nephew of former Phillies general manager and Red Sox first base coach Ruben Amaro. Rob Amaro’s younger brother, Andrew, was an assistant coach at Delaware in 2017. That season, at a time when Gragnani was a coaching assistant in the Red Sox system, Andrew Amaro kept mentioning a sophomore pitcher.
“He was saying, this lefthander, Brandon Walter, I’m telling you, is going to be really good,” said Gragnani. “I brushed it off, but then I got the scouting job [in 2018].”
Walter was a junior at the University of Delaware and draft-eligible in 2018, but there was a problem: He’d undergone Tommy John surgery after tearing his ulnar collateral ligament during the 2017 season. He didn’t pitch in games until 2019.
In that 2019 season, Gragnani’s chief responsibility was following Noah Song at the Naval Academy — a pitcher whom the Sox ended up drafting in the fourth round that year. But he didn’t forget the raves from Andrew Amaro.
“I’ll tell the truth straight up. If I hadn’t known [Amaro], I wouldn’t have kept tracking this kid,” said Gragnani. “But I had that history nugget, where I have somebody who’s seen this kid every single day really, really well.”
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Gragnani went to see the lefthander pitch against UNC-Wilmington, a team that featured a first-round talent (Greg Jones, whom the Rays drafted that year) as the leadoff hitter. Walter featured a pedestrian 86 to 90 m.p.h. fastball that day, touching 91 once. He pitched seven innings, allowing four runs on nine hits.
But Gragnani nonetheless saw a lot of what had captivated Amaro. He had a good build — 6 feet 3 inches and 195 pounds, with room to add more strength — and delivered strikes with his fastball as well as a changeup that the scout viewed as having the qualities of an above-average big league pitch — a 55 on the 20-to-80 scouting scale — and what Gragnani thought was a very good cutter. Walter actually intended it to be a slider, but it cut in on righties on a horizontal plane rather than breaking down. He also had a loopy curveball that he could throw for strikes.
Walter struck out 11 and walked one. While the lefty permitted nine hits, Gragnani noted that few were well struck.
“The pitchability, the command and control that game in particular were all double plus — like 60, 70 grade,” said Gragnani. “There was obviously some deception that adds something to his stuff. He was able to get swing-and-miss without power stuff. The hitters weren’t squaring him up.”
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Gragnani pegged the changeup as a 55.
“The one knock I had was the velocity and the stuff lacked power, but the hard things like throwing strikes and pitchability, throwing all four pitches for strikes, competing, going through adversity already, he had done all those things,” said Gragnani. “I’m betting if this kid adds velocity with the ability to throw strikes and a changeup that’s already plus, we might have something.”
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When the pandemic shut down the 2020 minor league season — the first full pro season of the lefthander’s career — Walter was determined not to remain idle. As the world started to reopen in the summer of 2020, he dedicated himself to improving his strength and conditioning, working diligently at the Titus Sports Academy in Delaware.
“Every week, it was kind of like, ‘OK, now I’m throwing 91, 92, 93, 94.’ It was just climbing as the winter is going, and the off-speed stuff ticked up along with it.”
The Red Sox kept tabs on their players throughout the year and checked in on their physical and mental well-being as well as to see what kind of baseball work the players had been able to do. Through FaceTime meetings, Green — the minor league pitching coach — had tracked Walter’s progress, which he relayed to other members of the team’s player development staff.
“Immediately, they’re like, ‘Whoa,’” Green said.
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By the time minor leaguers reported to spring training in April, Walter felt giddy with the sense of newfound possibility.
“I talked to [Gragnani] at spring training, and he was like, ‘Dude, what happened to you?,’” recalled Walter. “It was exciting to see the reactions from everybody, because before, I never got those reactions with just pure stuff.”
It wasn’t just that Walter had velocity, however. His low three-quarters arm slot — some describe it as similar to Chris Sale — tends to create a ton of side-to-side movement, with a sinker and changeup that dive to the lefthander’s arm side, and a slider that sweeps across the plate.
“There are certain guys where you’re like, ‘I don’t want to play catch with him, because nothing is true. Everything moves,’” said Green. “He’s a guy like that.”
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As promising as Walter’s spring had been, the team wasn’t quite ready to upend its plans based on what the 26th-rounder showed on the back fields in Fort Myers to open the 2021 season. Walter began the year in the bullpen of Low-A Salem, typically pitching two innings at a time for the first month of the season.
“When you’re a Day Three-guy [in the draft], whether you’re good enough or not, you’re not getting the same opportunities that a first-round pick is. That’s just how it works. I’m not like mad about it, but that’s just how it is,” said Walter. “For me, I kind of had to go the hard way, reliever first.”
But he dominated in a way that piqued the team’s interest to see if there could be more.
“When I was in the bullpen, I loved it. I bought in,” said Walter. “[But] I think I can do a lot of things as a starter to give hitters different looks multiple times through the order.”
Walter had worked to pitch to the edges of the plate in college and at the start of his pro career, trying to avoid contact. But given the uptick in the velocity and movement of his pitches, the Sox believed Walter no longer needed to be as fine. He could become more pitch efficient — and still often miss bats — by attacking the zone and putting hitters on the defensive, something the team drove him toward with data highlighting his effectiveness in all areas of the strike zone.
“He didn’t realize how good his stuff was. He was just trying to make a club, trying to scrap, trying to survive,” said Green. “He had to re-train his way of thinking, going from, hey, a guy that’s trying to make a club or a guy who’s trying to just fight for a job, re-training his way of thinking to like, ‘Let’s get this kid to Boston in a couple years.’ He has great stuff. He was having the success and getting the results you want.”
Walter moved into the Salem rotation in late June. He made two starts, striking out 15 batters with one walk while allowing one run in eight innings. That led to an almost immediate promotion to High-A Greenville.
He initially faltered — he allowed 17 runs and five homers in his first 12 innings spanning three starts. But there was also a lot of bad luck. Gragnani saw an amusing echo of the time he’d seen Walter at Delaware, when the pitcher struck out a ton of hitters, walked almost no one, and poorly hit balls kept turning into hits.
Walter quickly found his footing. Over his remaining nine starts in Greenville, he had a 2.33 ERA while holding hitters to a .166/.240/.209 line with one homer allowed in 46⅓ innings with 65 strikeouts (36.3 percent) and 12 walks (6.7 percent).
The performance combined with the pure quality of Walter’s pitches was remarkable. At 24 (he turned 25 in September), Walter improbably emerged as one of the team’s best pitching prospects. Some evaluators consider him one of the top 10 Red Sox prospects heading into 2022.
“I’m kind of behind the curve in the age thing. I honestly didn’t think there was any way I could get on those [prospect] lists being the age I am,” said Walter. “You don’t see too many people debuting on those lists when they’re 25. I do take a little bit of pride in that.”
Walter is likely to open 2022 in Double-A Portland. His profile is no longer defined by his selection as a 26th-rounder.
“I always joke with scouts, I got this kid way wrong . . . But I was probably the only one of the scouts that turned him in. So that gave us a chance,” said Gragnani. “It really was almost a lucky accident . . . It’s crazy. I think it shows how crazy the draft is. There are potential big leaguers all over the draft.”
Alex Speier can be reached at alex.speier@globe.com. Follow him @alexspeier.