PHOENIX -- There hasn't been a lot of good news for the D-backs lately, but the progress right-hander Zac Gallen is making on his rehab from a strained right elbow certainly qualifies.

Gallen, who went on the injured list on May 12, threw a 30-pitch bullpen session on Tuesday; he used all of his pitches and came out of it feeling good.

"For the most part, I was feeling pretty good for the past week and a half," Gallen said. "I was champing at the bit to get back on the mound."

Gallen said he will undergo a follow-up MRI on Thursday to get a sense of where his healing process stands.

"The medical staff just wanted to get some bullpens under my belt, see how the elbow and everything handled those types of stress," Gallen said. "From what I understand, the medical staff is saying, 'If you feel good and you’re having no issues, this MRI is going to confirm what you’re feeling and give us some clarity on the last few weeks.'"

Gallen is eager to get back out on a big league mound, but he understands there is a process that will need to take place beforehand. The organization is taking it week-to-week and there is no target date for his return yet.

Working in Gallen's favor is that he did not have to undergo as long of a shutdown as first feared when the diagnosis was initially made. However, watching his teammates drop 13 straight games and go 5-24 in May was excruciating.

"It kind of [stinks] that I can’t be out there doing my part," Gallen said. "As corny as the saying is, 'The best ability is availability.' It stings in a sense that we’ve had a rough patch. But I know the guys are grinding. That’s the thing. the guys are grinding and doing the best they can. Sometimes, the breaks just don’t go your way. I think that’s what’s been our deal so far. We’ve lost some one-run games and that’s tough. Those can make or break a season, if you’re successful or unsuccessful in those one-run games. A lot of times, the baseball gods aren’t on your side. Hopefully, we can get out of this funk and turn the page here in June."