SCOTTSDALE, Ariz. -- Even when you're one of the best pitchers in baseball, there are always things that you can work on during Spring Training.
D-backs ace Zack Greinke threw three shutout innings in Wednesday's 8-4 win over the Padres, but even before the game ended he was already thinking about what he needed to improve upon for the next time he takes the mound.
"I was a little uncomfortable with guys on base," Greinke said. "I didn't do as good with guys on base and hopefully the next time I'll be a little more comfortable with guys on base. I just wasn't as comfortable or just didn't feel as comfortable on the mound. I don't know if the pitches were that much worse or just the same, but I just didn't feel as in control as when there was no one on base."
Greinke gave up four hits over his three shutout innings, but three of the four came on grounders and the fourth was a soft liner to right.
In the second inning, after Greinke retired Matt Kemp, he allowed three straight singles to load the bases, which provided Welington Castillo with a chance to help Greinke get out of the jam.
"I want to be there when things are not going well, too," Castillo said. "So I can figure out what I can do to get him back to where he should be. That's good to have happen in Spring Training so when it happens in the season we can get through that."
Greinke got a popout and a groundout to end the inning.
In two spring starts, the right-hander has worked five scoreless innings.
"It's getting used to dealing with more complex situations and having to think about more things and being able to put it all together," Greinke said of the Spring Training learning curve. "Like I said, today it was a little quicker in my head than during the regular season. It was good experiencing that so hopefully it's better the next time."
Greinke also shared insight into his changeup.
Most pitchers like to have an 8- to 10-mph difference between their fastball and changeup, but Greinke's comes in at only a few mph slower than his fastball.
"When I throw my changeup 6- to 7-mph slower, it's not a good pitch," Greinke said. "Either my arm speed slows up or the movement isn't as sharp. Something makes it not a good pitch. I think ideally I'd rather have 6- to 7-mph difference, but I don't throw that well. I throw it well when it's only 2- to 3-mph difference. That's why I throw the harder one, because it's a better pitch overall."
Greinke threw 38 pitches, 24 for strikes, and after his outing threw several more pitches in the bullpen because he had not reached his pitch limit for the day.
Steve Gilbert is a reporter for MLB.com. Follow him on Twitter @SteveGilbertMLB. This story was not subject to the approval of Major League Baseball or its clubs.