"It's a tribute to Wes and his work ethic," said Caserio, who added that Welker passed his physical before taking the field.
"I'm not fully there," Welker said. "We're getting closer. I can't point out one thing. I think I can get better at a lot of things, whether I was 100 percent or not. We're working toward that."
Welker said his knee and the shoulder he injured during the season, forcing him to miss two games, both feel great. He also said he didn't know when he would be cleared for contact, leaving it up to coaches and doctors.
Welker said he wasn't really thinking about the knee during drills, although he would continue to wear the brace that he sported Sunday at least for a while.
"Obviously if I was favoring it (the knee) or something, I wouldn't be out here," he said.
Welker said there was no chance to relax in the offseason as he rehabbed.
"There was no vacation time," he said. "A nice weekend here, a nice weekend there, or anything like that. It was six hours of work each day, making sure I was bringing it every day, and that was the toughest part."
Welker had surgery in February, one month after he injured the ACL on the fourth offensive play of a 34-27 loss at Houston in the regular-season finale. He also damaged his medial collateral ligament, which didn't require surgery, on the play when he planted his left leg after making his NFL-leading 123rd catch of the season.
However, Welker recovered quickly, participating in agility drills and catching passes while wearing a brace on his knee during organized team activities June 2. Now Welker is OK to participate in training camp.
Notes: Caserio deflected questions on any possible negotiations with All-Pro guard Logan Mankins, who is holding out after refusing to sign a contract during the offseason. "I'm not going to get into that," Caserio said. "We're focusing on the players that are here." ... Caserio also said he expects a resolution soon on LB Derrick Burgess, who hasn't reported to camp and reportedly is contemplating retirement. Burgess, who had five sacks last season, signed a one-year, $1.5 million contract during the offseason. Because of Burgess' failure to report and WR David Patten's retirement, the Patriots have two open roster sports for the time being.
The Associated Press contributed to this report.