PHOENIX -- There is a strength to Brandon Pfaadt. Yes, the D-backs right-hander has the prototypical strong body you like to see in a pitcher -- 6-foot-4, 220 pounds -- but the first thing that those within the Arizona organization are apt to mention when discussing him is his internal fortitude.

It was that strength that helped him rebound from two disappointing starts to open his big league career and hold the Giants to just one run over five innings in a 2-1 Arizona win on Sunday that was capped by Lourdes Gurriel Jr.'s walk-off RBI double in the ninth.

Pfaadt, the D-backs' No. 3 prospect, was called up from Triple-A Reno two weeks ago, and in his first two starts he allowed 13 runs in 9 2/3 innings.

That’s not the way you want to begin your Major League career and it can rattle a person’s confidence. But not Pfaadt.

“Everybody expected him to come up a puddle of mud or something like that,” pitching coach Brent Strom said. “You know, he's very strong and he believes in himself and he's had success throughout his career. I told him even after those first two, I said, 'I've seen a lot of pitchers in my day and I really believe this guy is going to be a good one eventually.' Really, really good. And I just love the way he's poised -- he doesn't get too high or too low. There's a calmness about him, which I didn't have when I was pitching and a lot of guys don't have.”

It was clear from the get-go that Pfaadt didn’t have a hangover from his previous two starts as he struck out the side in the first inning.

It set the tone for the day, Strom said.

The only run Pfaadt allowed came in the fourth when Michael Conforto homered to right. Pfaadt walked the next two hitters before retiring the side with no further damage.

“It was tough,” Pfaadt said of the way his first two starts went. “But at the end of the day, you've got to trust yourself and bounce back. So that was the name of the game today. It's just how I've been taught and how I’ve been coached and it just doesn't really affect me. The past is the past and you’ve got to move forward so that’s kind of how I think about it.”

Following his last start against the Marlins, manager Torey Lovullo had a talk with Pfaadt.

“I basically told them after the last outing that he's much better than that, and we got to figure out how to make it work,” Lovullo said. “And he took that as a personal challenge and it showed up today.”

While Lovullo handled the mental side of it, Strom and assistant pitching coach Barry Enright looked at the mechanical side of things.

Enright discovered on the TrackMan system that Pfaadt was not keeping his fingers on top of the ball when throwing his fastball. Instead, he was just a tad off to the side. It seems like a small thing, but when that happens, the pitch doesn’t have the same late life to it and is easier to hit.

“I think we focused on getting on top of the fastball and throwing it downhill,” Pfaadt said. “I think that was a huge adjustment from the last time. I think it was getting too rushed and we made that adjustment down in the bullpen and I felt good today.”

The extra “hop” that Pfaadt got as a result of staying on top of the ball was noticeable to the Giants hitters, even Conforto.

"His fastball was jumping,” Conforto said. “He had really good spin on his breaking stuff. His fastball was effective at the top of the zone. You try to bring him down, but he’s also got a pretty good curveball, so if you’re bringing him down, he can throw that thing at you. He did a good job. He didn’t make a whole lot of mistakes. He definitely brought it today."