MIAMI -- Phillies reliever David Robertson took a big step in his recovery as he eyes a late-July return.

Robertson, on the 60-day injured list with right elbow soreness, threw 20 fastballs and a "couple easy changeups" off the mound for the first time on Sunday morning at Marlins Park.

"My command was better than I thought," Robertson said. "Velocity's not there yet. I'm going to have to build up a little bit. I originally told you guys that velocity would be around now, but I'm coming to grips with it -- that I'm going to have to build back up enough to get a little stronger. I don't think I can go out there and compete anytime soon with what I'm featuring. It's not hard enough, not for this level."

The 34-year-old right-hander will attempt another bullpen session on Wednesday in Atlanta and work through the All-Star break.

It comes as much-needed progress after setbacks for the 12-year veteran. Robertson last pitched on April 14, recording two scoreless innings in Philadelphia's 3-1 win in Miami. He took three weeks off before trying to play catch in mid-May in Kansas City. When that didn't go well, Robertson spent three weeks building his strength in Clearwater, Fla. From there, he began throwing, progressing from just tossing to playing catch from 90 feet.

"Right from the get-go, I thought I was only going to be down 10-12 days," Robertson said. "I've never had anything like this. I think more realistic is the end of July. Could be sooner, could be later. I'm targeting that last week of July just to be ready."

Robertson, who signed a two-year, $23 million contract this offseason, made just seven appearances before being sidelined. Philadelphia's bullpen could use his late-inning experience (147 career holds and 137 saves). The relief corps has the fourth-lowest WAR in the Majors (-0.1).

"I don't know if you've looked at my track record, but I like to be out there, I like to play every day," Robertson said. "I like the opportunity to be in every game. It's been frustrating and different for me. My longest stint I've ever had on the IL was 30 days back in 2012. I remember it because I couldn't take it. I can't stand it.

"I'm watching everybody here, and I love being with the team, but I want to be out there with them pitching, helping get outs. It means a lot to be out there on the field, and I'm trying to get back out there now. Mentally, I'm getting through it. I'm adjusting. I'm trying to stay mentally strong so I can get back really quick."