SANTA CLARA Wide receiver Chris Owusu stood out Friday because he was one of the few 49ers who wasn't doubled over.
The opening practice of Jim Harbaugh's three-day rookie minicamp was a grueling affair designed to acclimate the incoming crop of players to the pace of practice when the full squad assembles later this month.
That pace tested a number of players' lungs and hamstrings, but not those of Owusu and several other Stanford products who were prepared for what was in store.
"I played with coach Harbaugh for three years," he said. "I know what he expects from his players. I know his mentality; I know his philosophy. And part of it is, you can't be competitive if you're not in shape. I wanted to come in here and be in shape."
Owusu stood in contrast to fellow wideout and first-round draft pick A.J. Jenkins, who was seen sagging and gasping for breath from the midpoint of the session onward. Jenkins said he'd been working out regularly in his native Jacksonville, Fla., but acknowledged he was not ready for his first NFL practice.
"I'm back home and thinking I'm in shape working out in the morning time," Jenkins said. "You definitely see (this) is a totally different ballgame, so you've got to get your mind right."
Said Harbaugh: "The good news is that it's a very talented group of young receivers. You could tell that right away. But the bad news is we've got to get them in shape. I don't know exactly what all these guys have been doing in the last six months."
Harbaugh said his reaction may have been influenced by having watched his veterans whom he described as "fanatical" in their conditioning for the past month. Indeed, the first rookie practice likely was meant to be a wake-up call for the roster competition that lies ahead.
To his credit, Jenkins bounced back nicely for the afternoon session. And he said he was even more eager to get together with Jerry Rice and run the hill in the foothills above San Carlos that the Hall of Fame wide receiver made famous during his career. Jenkins and Rice have been exchanging giddy tweets all week about their plans.
Harbaugh didn't think it was a bad idea.
"I don't think it ever hurts to be around Jerry Rice," he said.
Hornet watch Count former Sacramento State quarterback Jeff Fleming among the rookies who found the morning practice mind-boggling. Fleming said he had to process concepts he hadn't run since community college.
"The first practice was really nerve-racking, but by the second practice, I calmed down a little bit and really had a better idea of what was going to happen on plays and everything," he said. "It's going to get better as we go, but they're going to throw a whole other load of stuff at us (today)."
Fleming faced Harbaugh's Stanford team in 2010, and he said the coach remembered the game. Does he think that's why he landed in Santa Clara for a tryout this weekend?
"I really don't know," he said. "I don't ask questions. The fact is he let me get my foot in the door, and I just want to take advantage of that, if it's possible."
Et cetera Outside linebacker Darius Fleming's first practice ended almost as soon as it began. The fifth-round pick tweaked his hamstring early and sat out the session.
Center Chase Beeler, who spent 2011 on the 49ers' practice squad, broke his right hand recently while lifting weights and is not participating in the current minicamp. Beeler will have his cast removed in two weeks, Harbaugh said.
Harbaugh said he was impressed by second-round pick LaMichael James' initial practice: "He's just got a great look in his eye, and he's got an enthusiasm out here," he said of the former Oregon running back. "I can tell he's got a real like for football. So far so good."