He rolled his left leg in a collision with Jason Banks late in the workout and was taken off on a cart. He was smiling as he left and the team said they were looking at his left ankle. It wasn't known how serious the injury was.
A slimmed-down Wells arrived at the Cardinals training camp in the wee hours and set his sights on winning the starting running back job by the time the season begins.
"I'm the type of guy that I like to get the ball and I like to get it often," he said at a news conference. "I haven't thought about sharing carries too much. I'm just going to get here and work hard and hopefully come out of camp that No. 1 guy."
Wells had already been in camp for a few hours when the Cardinals announced that they had agreed to terms with the Ohio State back, their No. 1 draft pick and the 31st selection overall. He took his physical on Friday and said he arrived at camp about 3 a.m. Saturday.
"We tried to actually get him to stay and just come in this morning," coach Ken Whisenhunt said, "but he seemed determined to get here."
Wells had been waiting in Phoenix for his agent Todd Frances to work out the details of the five-year contract. The deal is worth $11.8 million, $6.3 million guaranteed and the fifth year is a team option.
"I was stressing my agent," Wells said, "and just telling him to get things rolling and get me in there."
Cardinals coaches wanted Wells to trim his weight, and he arrived in camp at 224 pounds, down from the 246 he weighed when he first arrived in Arizona shortly after the draft.
"That was the most I had ever been," he said. "I blame it on the NFL for sending us around to all those different teams and they were feeding us like crazy."
Wells said his playing weight at Ohio State was about 238.
"I feel great," he said. "I definitely want to stay at this weight. I feel a lot faster and quicker and I don't get tired as much."
Whisenhunt said that the coaches felt that the slimmer weight would be best for Wells' body type.
"Give him credit. It's not always easy to do that," the coach said. "A lot of times rookies don't understand the sense of urgency that you have to have as far as coming into training camp in shape."
"But as we've shown in the past, we're going to have competition at positions and we're going to play players that give us the best chance to win," Whisenhunt said.
Wells is being counted on to help what was the worst running game in the NFL during the regular season.
"The only personal goal I've set for myself is to be that guy," he said. "I know we're a passing team but defenses will actually have to focus on the running game with the Arizona Cardinals as well as the passing game."
Wells participated only briefly in minicamp and couldn't take part in the voluntary workouts because his Ohio State class was still in session. He has been befriended by Larry Fitzgerald, attending the All-Pro receiver's camp in Minnesota and staying at his house while the voluntary workouts were going on.
"I don't know a better guy than Larry. He's taken me under his wing," Wells said. "Larry's the type of guy that's going to stay on me. He's stayed on me since I got here. ... He has one focus and you can clearly see it and it's getting to another Super Bowl and winning it."
To make room on the roster for Wells, the Cardinals released tight end Alex Shor.