"It will be a good first step," Thatcher said.
There have actually been quite a few "first steps" for the left-hander since having surgery to shave down his frayed labrum and rotator cuff and to remove the bursa sac in his left shoulder.
Thatcher played catch on June 12 for the first time since surgery and has progressed since then, throwing on flat ground and then throwing on flat ground with intensity.
On Wednesday at PETCO Park, Thatcher increased the intensity of his throwing program, as he threw 25 pitches where "I kind of let some of them go pretty good."
"It's felt good ... there's been no discomfort," he said.
Thatcher was sidelined most of Spring Training because of soreness in his left shoulder and then started the season on the 60-day disabled list, retroactive to March 22.
A year ago, Thatcher was one of the top left-handed specialists in the National League, posting a 1.29 ERA in 65 games.