It was the first time Happ threw off a mound since he suffered a setback doing so two weeks ago. Phillies pitching coach Rich Dubee was optimistic about the outcome of the session.
"Today was a big hurdle," Dubee said. "This is where we got to last time, and he didn't respond very well. He responded much better today."
Happ, who has been out since April 16, will rest for the next few days and then, assuming no setbacks, will throw another bullpen session in three or four days. He threw all fastballs on Monday.
"[Tuesday] will be a good test," Dubee said.