Bruins coach Jim Mora was visibly concerned about Lucien after the afternoon practice at training camp in San Bernardino.
"As always, we're going to be overly cautious with anything that has to do with the head, neck or spine," Mora said. "That's not a toughness issue, but we're praying for him and thinking about him. He's in good hands."
The Los Angeles Times reported Lucien hit his head on the ground during a drill, was taken to the hospital and released later Tuesday. A source in the football program told the Times that Lucien is expected to rejoin the team for Wednesday's session.
Lucien started three games as a sophomore last season, catching 19 passes for 339 yards and two touchdowns. He is a strong candidate to be a starting receiver for quarterback Brett Hundley this season opposite Jordan Payton.
Lucien is an athletic junior known for acrobatic catches in practices and games.
"I believe it was when he was making one of his rather spectacular, but sometimes typical, Devin Lucien catches that we've kind of grown accustomed to seeing," Mora said. "It shook him up a little, so we'll find out the extent of it."
The Associated Press contributed to this report.