Happ made two starts for the Phillies before being put on the DL with a left forearm strain on April 22. The 27-year-old, who went 12-4 with a 2.93 ERA for Philadelphia last season, made six rehab starts and was 1-1 with a 6.93 ERA.
General manager Ruben Amaro Jr. and pitching coach Rich Dubee agreed that Happ's progression wasn't where they wanted it to be, and they weren't ready to squeeze him into Philadelphia's rotation, which has been pitching decently.
"I was honest with him," Amaro said. "I think he just wasn't pitching well enough to be in our rotation right now. I think he will be soon. But just from the way we evaluated him and the way he threw, he's making progress, but not well enough to break into our rotation at this time."
Happ's velocity appeared to be fine, but his consistency of command in the strike zone wasn't there. Both Amaro and Dubee expressed optimism that Happ will be able to return to the Major League club and help from the rotation at some point this season.
"I just told him, 'Don't waste time down there,' " Dubee said. "Hopefully he gets down there and throws a bullpen [session]. He should get down there and work to get back up as soon as possible."
When asked what Happ needs to work on most, Dubee said the hurler needs to get more reps.
"If he's being truthful, and he's healthy, he needs reps," Dubee said. "You don't just pick a baseball up and [say], 'Here I am.' "
The Phillies could have applied to extend Happ's rehab stint, but Happ did not suffer any setbacks health-wise.
"He's got a lot of reps now, even maybe more than he would in Spring Training, so he should be ready," Amaro said. "But he's just not pitching as well as he has in the past. I think he will."
Zach Schonbrun is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.