Anticipation is growing for Red Sox pitching prospect Brayan Bello’s major league debut Wednesday

Righthander Brayan Bello heads for the clubhouse before Tuesday's game against the Rays at Fenway Park.Jim Davis/Globe Staff

When Brayan Bello takes the mound Wednesday, he will do so as the most anticipated Red Sox pitching prospect in years. Not since Eduardo Rodriguez in 2015 has a Red Sox minor league pitcher arrived in the big leagues with as clear a path to being a rotation anchor.

That Bello occupies that space almost exactly five years after signing with the Red Sox represents a remarkable development. He was a passed-over prospect on the international market who was overlooked by all 30 organizations for his first two full years of eligibility to sign. When the Red Sox finally inked him as an 18-year-old July 2, 2017, he signed for less than $30,000.

“I just took it as a challenge knowing that I wasn’t ready at [16] to sign and play professional baseball,” Bello said recently. “I took that year and a half to get more strength in my body and perform the right way so the chance eventually would come.”

Red Sox Dominican scout Manny Nanita started building the team’s history with Bello when he was 17, identifying the then-slender righthander (Bello once recalled that he was 6 feet and 130 pounds at the time of signing) as a pitcher whose athleticism, quick arm, ability to throw a breaking ball, and competitiveness would appeal to the Sox.

The Sox had a chance to work him out at their academy in the Dominican. There, while his velocity was relatively modest (high-80s to low-90s), several team evaluators saw a player with impressive feel to pitch and for whom a velocity increase was easy to forecast when he got into a professional strength and nutrition program.

“He caught your attention quick,” said assistant GM Eddie Romero. “It all comes down to Manny Nanita seeing him at his agent’s place and saying, ‘This guy checks a lot of the boxes of what we look for. You guys need to see him.’ ”

The Sox were impressed not just with his stuff and standout arm speed but also by the determination of a pitcher who remained unbowed despite the long period preceding his signing.

“You could see the kid was on a mission,” said Red Sox co-director of international scouting Rollie Pino.

That same sense fueled Bello’s rise once in the Sox system. He immediately impressed Latin America field coordinator Jose Zapata with his maturity and responsiveness to instruction.

“He listened to everything. He never said no,” said Zapata. “He just said, ‘I want to run. I want to pitch. I want to be a big leaguer.’ ”

As Bello gained size and strength, his stuff ticked up beyond any expectations of the Red Sox. His fastball reached the mid-90s by 2019 in Single A Greenville — and then, after Bello proved diligent in his self-managed workout program during the COVID-19 shutdown year of 2020 — the high-90s by the time he arrived for instructional league in the fall of 2020.

He turned his curveball into a slider — an offering that seemed to work better with his arm slot and ability to throw hard. And he developed his changeup — a pitch for which he had some feel when working out at the Sox academy in 2017 — into an offering with the arm speed to sell to hitters as a fastball.

And then came the pièce de résistance. Late in 2021 while Bello was in Double A, he started to incorporate a mid-90s sinker so that he could work at both the top and bottom of the strike zone with his premium velocity.

In short order, that pitch became a jaw-dropper, an offering at 95-98 miles per hour that Bello leaned on in Triple A Worcester this year at roughly a 35 percent rate. He became relentless with the sinker, unafraid to throw it in the strike zone, where its tremendous, late life resulted in swings-and-misses as well as a grass-cutting succession of groundballs — a formula for dominance.

“That’s what makes Bello special,” said WooSox hitting coach Rich Gedman. “He can beat you in the zone. Not a whole lot of people can do that.”

Nor are there many pitchers who take the mound with Bello’s presence. He commands the stage in a way that typically characterizes the best prospects. A pitcher who was undeterred by his long road into pro ball likewise has proved unflappable in the face of game stresses.

“I don’t think he’s going to be fazed by anybody,” said Pino. “He’s got Pedro Martinez type of makeup. He ain’t scared of nobody.”

Between Double A Portland and Triple A Worcester this year, Bello forged a 10-4 record and 2.33 ERA. Among minor leaguers with at least 70 innings, Bello ranks second in strikeout rate (33.7 percent) and first in groundball rate (63.1 percent).

Reviews of his work in Worcester have been breathless.

“What a stud,” said outfielder Rob Refsnyder. “He’s the real deal. It’s hard not to get excited watching him.”

Bello remains a work in progress. In particular, his ability to execute his slider to the glove side of the plate represents a milestone that could elevate him to a potential No. 2 starter or even an ace.

Of course, that outlook is part of the long game. For now, Bello has arrived at a point where he is ready for the first time to take the stage at Fenway against the Rays. Manager Alex Cora cautioned that one shouldn’t put too much stock in a player’s performance in his big league debut — that the novelty of the environment can twist the performance in ways that are not reflective of abilities.

For Bello, the greater significance of Wednesday is as a new beginning following a hard-earned opportunity. Once overlooked, the righthander insists that he is prepared for a new challenge.

“I’m ready right now,” said Bello. “I just can’t wait to get out there.”