Smith was drafted in the first round by the Eagles, with Kelly putting him through his paces during their pre-season fixtures, only to be left still scratching his head as to how the youngster will fare when the season gets underway next month.
"He's got a burst, he's got some speed coming off the edge. But if you're going to play that many plays, we're going to need more production out of you," said Kelly, according to The News Journal.
"[He's] still working at it, still got a lot of things to improve on. That's what the pre-season is all about."
The Eagles get their NFL campaign going against the Jacksonville Jaguars on September 7.