BOSTON -- A surprised Rick Porcello laughed when told the strikeout-to-walk ratio of a 21-year-old Red Sox minor leaguer from the Dominican Republic who most fans don't know.

"Wow. What's this kid's name?" Porcello asked.

Meet Denyi Reyes, a righty who Boston signed July 2, 2014. He has struck out 137 and walked 15 in 141.1 innings between Low-A Greenville and High-A Salem this season. That's an eye-popping 9.13 strikeout-to-walk ratio.

He has 278 strikeouts and 29 walks in 313 innings over four minor league seasons (2015-18) for a 9.59 strikeout-to-walk ratio.

"That's incredible," said Porcello who led the major leagues with a 5.91 strikeout-to-walk in 2016 when he won the American League Cy Young.

Red Sox ace Chris Sale, the leading candidate for the 2018 AL Cy Young, is third in the majors with a 6.64 strikeout-to-walk ratio.

"That's impressive at any level," Porcello added. "That's impressive at the high school level let alone professional baseball for a 21-year-old to be that effective."

The righty dominated again Thursday in his third start for Salem since his promotion from Greenville. He earned the win in Salem's 7-2 victory over Frederick. He pitched 7 innings, giving up two runs, four hits and no walks while striking out six.

He improved to 12-4 with a 1.97 ERA and .086 WHIP in 141.1 innings (24 games, 21 starts) between Greenville and Salem.

Reyes has pinpoint control. He has averaged only 0.9 walks per nine innings in 2018 and 0.8 walks per nine innings for his career.

Sale stared at Reyes' stats on Baseball-Reference.com.

"How many hit by pitches?" Sale asked after seeing Reyes' incredible walk totals. The Red Sox ace then answered his own question. "Four. Hmm. Send a message, too."

The statistics are remarkable across the board. But Reyes doesn't rank among the Red Sox's top prospects.

MLB.com ranks him the organization's No. 30 prospect. Reyes began the season not listed on SoxProspects.com's top 60, but the website now has him ranked No. 28.

Reyes won SoxProspects.com's Pitcher of the Month for May, June and July. He also won the South Atlantic League Pitcher of the Month for July.

"Might be one of those sleepers," Porcello said.

David Price had a different take.

"Not after you write this story," Price said about Reyes potentially going under the radar all the way to the big leagues. "There are going to be a lot of expectations."

Release point extension comparable to Yusmeiro Petit's

In his first professional season (2015), Reyes struck out 63 and walked three in 75 innings (15 games, 14 starts) for the Dominican Summer League Red Sox Team 2. That's a 21.0 strikeout-to-walk ratio.

Porcello pointed out Reyes' career ratio is right around Sale's in July. In four starts, Sale struck out 43 and walked four (10.75).

Sale, meanwhile, is impressed with how many innings Reyes has thrown this season (141.1) and the prospect's WHIP (0.86). Reyes has thrown only 4.2 fewer innings than Sale during the 2018 season.

"I'm not a big numbers guy, but those are good," said Sale who once referred to statistics as "kind of bogus."

Porcello remembers seeing Reyes at one point. "Is he the bigger kid?"

Yes, he's tall.

"He's huge. The first time I met him I was like, 'You are a big boy,'" Red Sox vice president of pitching development and assistant pitching coach Brian Bannister recalled, laughing.

The 2018 Red Sox media guide has Reyes listed at 6-foot-4, 209 pounds.

"He's opposing standing next to him," Bannister said. "I've gotta imagine being a hitter he looks really big out there on the mound."

Bannister compared Reyes to Athletics reliever Yusmeiro Petit, who has a 3.39 ERA in 74.1 innings this season. Bannister and Petit were teammates at Double-A Binghamton during 2005.

"He's had a 10-plus big league career," Bannister said about Petit. "And he's always thrown 90-92 (mph). But he gets amazing extension. Everybody says his fastball just plays up because he can just reach so far to home plate past the average guy. He's just really flexible."

Reyes' fastball has sat at 90-91 mph this summer. He reaches 92 mph at times.

"Jake deGrom gets way out there," Bannister added. "There are some pitchers that just because of the way their bodies work, they're releasing the ball like a foot past everybody else. Denyi Reyes is one of those guys."

'He just really locates'

Reyes has gone 2-1 with a 2.55 ERA and 0.96 WHIP in 17.2 innings (three starts) for Salem.

He's 32-6 with a 2.13 ERA, 0.93 WHIP and .222 batting average against in 63 outings (38 starts) during his professional career.

"That's good control, absolutely," Price said. "That's real nice."

But Price, who spoke with MassLive.com after Reyes' first start for Salem, pointed out A-ball hitters probably don't think they'll make the major leagues by walking.

"They want to swing. Umpires want to call strikes," Price said. "But 14 walks in 130 innings, 130 punchouts, that's pretty good. He's got at least three pitches that he controls for strikes I'm sure."

He features a fastball that cuts, a changeup, slider and curveball. He does a nice job of repeating his delivery.

"He just really locates his fastball, cutter and curveball," Bannister said. "Just big boy, strike thrower. Big extension, stays on line to home plate really well. Fills the zone. Knows how to cut the ball and make it move. Just really attacks hitters."

The control certainly is impressive. But "even more so" because of his age, Sale said.

On how Reyes' has allowed just 15 walks, Porcello said, "That's amazing."

"At the end of the day, if he's got one of those fastballs that guys don't pick up, if it's 90-91 and he's got stuff to go along with it, there's plenty of guys that are pitching in the big leagues that are having success with that," Porcello said.

Porcello pointed out how Giants' Johnny Cueto doesn't throw hard.

"Johnny Cueto has a 2.50 (ERA) every year," Porcello said. "You know? There's guys that can do it. He might be one of those guys where he's got crazy deception. And he's a strike thrower. So that's a great combination."

So many top prospects throw in the high-90s but lack command. Reyes doesn't feature a heater but his plus-control makes it look so easy for him.

"They're showcase prospects," Porcello said about young pitchers who throw hard but can't throw strikes. "They're not pitchers. Big arms with big breaking balls but when it comes to pitchability, that's what I'm talking about right there (with Reyes). That's incredible."