The D-backs' top prospect threw off a mound last Monday for the first time since last October's surgery.
Parker, the club's first-round pick in the 2007 First-Year Player Draft, threw 25 pitches, all fastballs, with the catcher crouched 55 feet away.
"It felt great," he said. "I have to tell myself to take it easy because it feels so good."
For right now, the plan is for Parker to throw similar sessions Monday and Friday each week, long toss Wednesdays and work in the weight room Tuesday and Thursday. He is rehabbing at the team's training facility in Tucson where he has spent most of the past eight to 10 months.
"We're starting to bump things up," the 21-year-old said. "I'm just trying to stay patient."