Webb has been on the disabled list with bursitis in his right shoulder since after his Opening Day start.
"It's not 100 percent yet, but it's getting better," Webb said. "I think it's going to continue to get better."
Prior to throwing the session, Webb played catch from about 155-160 feet. The next step for him would be to throw from about 165-170 feet on Saturday and then do another flat-ground bullpen session. It's possible, he said, that he could throw a bullpen session off a mound next Tuesday.
Webb said he was hopeful that he could be back before the All-Star break but said even if everything goes according to plan, "it will be close."
Steve Gilbert is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.