BOSTON -- The Brayan Bello who stood on the Fenway Park mound for five electric innings on Wednesday night was the one who garnered all the hype during his ascension through the farm system.

The growing pains Bello experienced in his first three starts are subsiding, and that was evident throughout his performance on a night the Red Sox lost, 3-2, to the Blue Jays in 10 innings.

“I was attacking the hitters and I was always ahead in the count,” Bello said after the best performance of his young career. “I’ve learned how to attack batters right now.”

Over five innings, Bello allowed two runs on six hits, walking one and striking out seven.

“He was excellent,” said Red Sox manager Alex Cora. “That was good stuff. We felt in Houston, he was turning the corner.”

However, in that relief outing in Houston on Aug. 3, Bello threw just 16 pitches before suffering a left groin strain that kept him on the injured list until Monday. What has keyed Bello’s turnaround isn’t an improvement of his stuff, but rather his grasp of the mental game.

“You can’t just stay on one side of the plate; you’ve got to mix it up. From pitch one, that was electric. Weak contact, swing-and-misses, four-seamers up, changeup. He was really good,” said Cora.

Veteran teammates Nathan Eovaldi, Michael Wacha, Nick Pivetta and Rich Hill have played a role in Bello’s improvement.

“I learned a lot from the veteran players here. They taught me how to prepare, to face a team and how to prepare and have a good routine in between starts. So that’s been a huge help for me,” said Bello.

In particular, Bello cited Eovaldi.

“I’m very thankful for him, for Nate,” Bello said. “I think the progress I’ve had since my last start right now has to do a lot with him. He’s been a huge help for me and he’s always been there to help me and I really appreciate it.”

Not only was Bello effective, but he was efficient, throwing just 65 pitches in his five frames. Of the 37 swings the Blue Jays took against him, they whiffed on 13 -- six of them coming on changeups.

“In the second part of the game, that’s when he started using it,” said Cora. “They made some adjustments, started getting to some pitches down and in. [Pitching coach Dave Bush] went out there and talked about mixing it up. He started using the changeup, but was still using the four-seamer. That strikeout to [Matt] Chapman I think it was, 0-2, four-seamer, 97, 98, swing-and-miss.”

That will play at any level.

Working ahead is what allowed Bello to go to that changeup.

“It helped me a lot when I had to use it,” Bello said. “It worked really well and it was good for me to have the opportunity to use it and it was effective.”

The next step for Bello will be when Cora gives him the opportunity to go deeper in games. But that has to be gradual.

“We were talking about that when I took him out,” said Cora. “He hasn’t pitched five innings in a while, even before we called him up. He wanted more, of course. I love that. I told him, ‘You haven't gone five in like two months or three months.’ He smiled.”

Bello is ranked No. 3 in Boston’s farm system by MLB Pipeline, and is the top-rated pitcher.

With the Red Sox starting to fade from postseason contention -- they are seven back in the American League Wild Card standings with 38 games left in the season -- Bello should get regular work for the rest of the season.

His next start will come at Target Field on Monday against the Twins.

“I feel like tonight was a good step forward for me,” Bello said.

The Red Sox look forward to watching the many other steps forward that are likely to come from their 23-year-old righty.