FLORHAM PARK, N.J. -- Welcome to the NFL, rookie.
McKnight dropped a few passes, vomited on the field and had both calves cramp up.
"I felt a little dehydrated today, and didn't drink a lot water, so now I'm going to start drinking a lot of water and keep myself hydrated," an embarrassed McKnight said. "It was nerves. I was nervous at first, just getting back out, playing football and trying to show what I can do."
McKnight, drafted out of Southern California, felt better as the day's first practice went along and even showed off some slick, elusive moves.
"I thought Joe McKnight looked good," coach Rex Ryan said with a pause and a smile, "when he wasn't throwing up."
McKnight vomited near a goalpost midway through practice, and later had both calves worked on by team trainers.
"A little anxiety kicked in and all that kind of jazz and you probably haven't worked out as much you normally should, and those things happen," Ryan said. "He did look good running the football, but he had some drops and that kind of stuff."
McKnight, who said he never vomited during a game or practice before, was hoping that was all behind him as he prepared for the day's second practice. He appeared to have no queasy moments in the afternoon session.
McKnight was often compared to do-it-all running back Reggie Bush at USC, something he said bothered him at times. He was assigned No. 25 with the Jets -- Bush's number with New Orleans -- although Ryan said that was unintentional.
"It wasn't my decision," McKnight said. "I thought I was trying to leave something, but evidently I'm still in the spotlight and in the shadow again. I'm just going to wear the number, not going to say anything about it, and try to be me."
McKnight discovered he was given No. 25 when he walked into the team's locker room on Thursday.
"Well, I was kind of mad at first," he said. "That comes with the territory, but after a while, you just let it go and go with the flow."
He said he's already worn the jersey, so he has no plans to change the number, last worn with the Jets by safety Kerry Rhodes.
"It's what you make of that number," Ryan said. "It doesn't matter. He's not compared to anybody else. Let's just go play. He's a New York Jet, and let's see how he does. Hopefully he'll be compared to Matt Snell one day. Totally different type, but who cares?"
New York traded its fourth-rounder (No. 124) and sixth-rounder (No. 198) to Carolina to move up to No. 112 last Saturday so it could take McKnight. His presence made Leon Washington, a player with a similar skills set, expendable as the Jets dealt the former Pro Bowl kick returner to Seattle.
"The first thing is we've got to settle him down a little bit, but I think he can do some of the things that Leon did," Ryan said. "He's got plenty of wiggle and he's got a lot of talent. I wouldn't compare him to Leon 100 percent right now, but I think he can definitely help us on offense."