"He threw the ball really well," D-backs manager Torey Lovullo said of Walker. "I was very encouraged. I know everything post-workout was very encouraging. We're going to see how he feels throughout the next day or two and kind of plan out the next part of his return."
Walker has been on the disabled list since May 20 after battling a blister on his index finger for a few starts.
While on the DL, Walker has done a number of treatments including hot/cold soaks, the use of a laser and various ointments. When he threw his first inning Tuesday he did so with his finger wrapped. After that, he pitched without it on.
"We took it off and then I started dialing it in and everything started to feel good, the ball was coming out really good," Walker said. "I threw some changeups and that was probably my biggest concern, because that's where I felt [the blister] the most was the changeup and that felt really good. We'll see how it responds [Wednesday], but as of right now, I feel pretty good."
Walker simulated three innings with a handful of D-backs hitters standing in against him. He threw 60 pitches plus another 20 or so in warmups.
Given that number, the team would feel comfortable with him approaching the 100-pitch mark if he were to start Sunday.
"Definitely," Walker said when asked if the blister was noticeably better. "Just touching it 10 days ago it hurt pretty bad. So it's a lot better now."
Delgado has done a nice job of filling in for Walker. In two starts, he has allowed three runs (two earned) over 9 2/3 innings while striking out 11 and walking just one.
"He's developed a lot of confidence and he's gotten a lot of big outs in a lot of crucial moments," Lovullo said. "And he's stepped into the starting role and didn't change a thing. That's a key. That's a thing we ask these guys to do, is not change what's working."
Steve Gilbert has covered the D-backs for MLB.com since 2001. Follow him on Twitter @SteveGilbertMLB. This story was not subject to the approval of Major League Baseball or its clubs.