Smith went down hard after colliding with a Ravens player during a kickoff drill. He got up slowly then limped to the sideline, where trainers examined him before the cart hauled him back into the team complex.
Smith, last year's first-round pick, is scheduled to undergo an MRI on Friday.
The Eagles have already lost three other outside linebackers. Defensive end Vinny Curry took the majority of snaps in Smith's place on the second team.
Smith, taken 26th overall in the 2014 draft, is trying to rescue his career after barely playing last year as a rookie and having his position switched inside linebacker to compensate for injuries there.
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