SCOTTSDALE, Ariz. -- Zac Gallen began throwing his bullpen session on the six-pack of mounds at Salt River Fields last weekend, flanked by a pair of other pitchers. Those two finished up and another group of three pitchers began to throw.

Gallen remained.

The trio wrapped up its session and headed in, replaced by another three.

Still, Gallen remained.

Asked afterward if he threw a complete game’s worth of pitches, Gallen shook his head.

“I threw the same as everyone else -- 30 pitches,” Gallen replied.

What took Gallen so long to throw those 30 pitches is part of what makes him a perennial Cy Young Award candidate -- an attention to detail and quest for perfection. He’s not just getting through his bullpen to check it off the day’s to-do list, he wants to make sure he gets something out of every pitch of his session.

“You only get so many throws a day, whether you're playing catch or on the mound,” Gallen said. “I’m not going to waste them. So I have intention and purpose with those pitches. It's my time to get to practice what it's like to actually be on a slope. So for me, I'm going to try and have the best intention and purpose when I'm out there.”

It doesn’t go unnoticed by his teammates, who are used to seeing Gallen's marathon sessions.

Veteran right-hander Zach Davies also puts a lot of time and attention on his bullpen sessions in his own right -- but not even he can match Gallen.

“It's cool to see someone have the patience and thoughtfulness and awareness to be able to do that,” Davies said. “It's something that people can learn from if they’re paying attention. It’s not necessarily something that works for everybody, but you can pick pieces from it, you can find something out of it that helps you out. He spends a lot of time, and for me, I need breaks, I need the ability to just rest and relax and flush a bullpen and then come back to it. But for him, that's the way his mind works, and the ability to continue to do that is impressive.”

When Gallen throws a pitch during a session that isn’t quite perfect, he will take time to look at the TrackMan data to see how the pitch came out of his hand. It’s early in Spring Training, so he’s still trying to get a feel for his delivery. That takes time as well.

When he was in college at North Carolina and during his Minor League and early big league career, Gallen would throw a lot between starts. But like most pitchers, as the innings have piled up on his arm, he’s had to cut back on the amount he throws. That’s why, during the regular season, he puts a great deal of focus and effort into every session of playing catch or time spent throwing in the bullpen, in order to make those throws count.

Gallen finished fifth in the NL Cy Young Award voting last year when he posted the lowest WHIP in the NL at 0.913 and an ERA+ of 158. He had a 44 1/3-inning scoreless streak last year -- the longest in D-backs history and the seventh longest in AL/NL history.

“He’s very meticulous and thorough in his work, and I think that's why he's a great pitcher,” catcher Carson Kelly said. “That's why he can go on a run of [44 1/3] innings in a row without giving up a run. You can see the attention to detail in between starts. He’ll say, ‘I'm going to work on this because we're facing this team and this pitch is going to be very important for that.’ He does his homework and then puts in the work in the bullpen.”

No matter how long that work takes.