"Spirits were extremely high on the turf at Chargers Park yesterday, but the late burst of enthusiasm may have had less to do with the imminent end to training camp than the sight of the newcomer to passing drills, a tight end coming off the physically unable to perform (PUP) list. "I hadn't put the pads on since the Patriots game," said Antonio Gates, referring to the AFC Championship Game at New England that he basically limped through as an ill-disguised decoy. "It was fun. I was excited. Needless to say, though, I've got a lot of work to do." Gates, the Pro Bowl tight end who's averaged nearly 80 catches and more than 10 touchdowns over the past four seasons, has been brought along slowly from the toe injury he sustained in last year's divisional playoffs. He first ran some warm-up routes before Saturday's exhibition game at St. Louis, but only received medical clearance to participate in drills yesterday, and he was withheld from team drills. "It was a challenging situation, because for one thing, that was the first time in my whole career that I wasn't out there with the team," said Gates. "I was able to do some mental reps. Now I'm able to do some things physically." Whether he'll be ready to play in either of the final two exhibitions next week - and whether coaches will let him play against Seattle on Monday or at San Francisco on Aug. 29 - is unknown and seemingly unlikely. However, the fact he was making strong cuts and catching passes yesterday supports coach Norv Turner's steadfast assertion that Gates would be play-worthy for the Sept. 7 opener against Carolina. "Offensively, timing and chemistry are critical," said Gates. "To be out there with the receiving corps, the running backs, the tight ends, it just felt like it was about that time." At about the same time, the defense also was boosted by the return of another of the Chargers' top veterans to the practice field. Defensive end Luis Castillo, sidelined with a nagging back, returned and took part in both sessions. "If it were the regular season I'd be playing," Castillo said. "We're being smart with it.""