The injury occurred during a special teams drill. The Eagles were on kickoff coverage while the Ravens were returning the kick. Smith limped off the field after the play, seemingly favoring his right leg. After getting looked at by trainers, Smith was carted off the field.
No further details are known about Smith's status at this time.
The Eagles have been hit hard at outside linebacker this offseason. Travis Long suffered a torn ACL early in training camp. Smith, if healthy, is expected to serve as the team's No. 3 outside linebacker behind starters Connor Barwin and Brandon Graham. Smith obviously had a disappointing rookie season after being selected in the first round of the 2014 NFL Draft, but he showed signs of progress during the Eagles' preseason game against the Colts.
UPDATE: For what it's worth:
I understand Marcus Smith will get an MRI on his right hamstring. So, not good but could be worse— Les Bowen (@LesBowen) August 20, 2015