READING — The emergence of Austin Davis as one of the Phillies' top bullpen prospects has been one of the most promising signs from the first half of the minor-league season. And the relief pitcher said his growth has resulted from conversations he had this spring with retired star Roy Halladay.

Halladay, the former Cy Young winner, returned to the Phillies in spring training as a volunteer guest instructor, a role he continues to perform at the team's complex in Clearwater, Fla. Halladay's focus has been on baseball's mental side, something Halladay delved into after facing struggles early in his career. It is that aspect of the game that Halladay stressed with Davis, a lefthander at double-A Reading and one of Halladay's first pupils.

"I remember watching Roy Halladay, and now seeing him face-to-face and talking like he's just another guy … " Davis said. "He's eating a sandwich. I'm eating a sandwich. 'Man, this is Roy Halladay.' It's pretty cool."

Davis and Halladay often sat together in the Clearwater clubhouse or discussed the game on the back fields. The connection was easy, Davis said. The 24-year-old lefthander has allowed just four earned runs in 14 games since being promoted in May to Reading. He has struck out 24 batters and walked seven in 21 2/3 innings. Davis throws a slider and change-up and could push his way to the majors by the end of the season. Halladay's advice helped him prepare for that journey.

"My stuff is my stuff. It's good. I feel like it's stuff that I can pitch in the big leagues with," Davis said. "It's just doing it every single day, and that's what he helps you with. It was the same for him when he first came up. He had the stuff. He just didn't have the mental approach. He went back down all the way to A ball and built his way back up. He was stronger mentally for that. He's trying to help us with that without having to go through those struggles."

The Phillies drafted Davis in 2014's 12th round. He was a starter at Cal State Bakersfield but transitioned quickly to the bullpen. He is now one of several promising arms at double-A and triple-A.  Thomas Eshelman, a righthanded starter, and Jesen Therrien, a righthanded reliever, are creeping toward the majors at triple-A. Righthanderd starter Drew Anderson and righthanded reliever Alexis Rivero join Davis at double-A. Joe Jordan, the Phillies director of player development, said Davis still has a chance to be a starter.

"I see a guy that's been extremely aggressive," Jordan said. "I probably didn't expect it to go as well as it did in the first six weeks or so. He's been the same guy all spring. He's attacking the zone. He'll have nights where he shows major-league weapons, and he looks the part. We're just trying to build his consistency."

Halladay said in spring training that he was itching to get back into baseball. He retired in 2013 after four seasons with the Phillies. Jordan said Halladay is "a credible voice for our players." Halladay works under Geoff Miller, the team's first mental skills coach. Halladay has been around for just four months and is not technically a Phillies employee. But his results are starting to show.

"He has a lot of experience. He pitched a lot of innings. He knows what he's talking about," Davis said of Halladay. "He takes the concepts that we learn about being mentally strong, and he just has a way of it being more applicable to us at a deeper level than it already is. He knows what you really mean when you're saying something. It's like you say something and maybe you're holding back or being reserved, and he'll say 'No, this is what you really mean. Let me help you out with that.' He's been through it himself. He's had ups. He's had downs."