The Eagles needed a spark -- with 2:02 left in the game and down 21-16, the team decided to throw DeSean Jackson out for a punt return. We've seen him make a few big punt returns against the Giants in the past, so that's where the inspiration likely came from for the decision.
Jackson fielded the punt and gained 15-yards, but not the way he would have wanted to. He took a shot to the head (which was called for a personal foul) and when down on the ground he was hit a second time. When he was hit the second time, his foot got caught on the turf. He slammed his helmet on the field and had to be helped off the field without putting any weight on his right leg.
The initial fear from fans and media was a torn ACL or some other kind of major knee injury. Jackson took to Instagram after the game and posted a picture of him wearing a walking boot.
Walking around on that leg later in the night is a pretty good sign, and obviously, a walking boot means the injury is either to his foot or his ankle.
According to Dr. David Chao (AKA "Pro Football Doc"), he is suspecting from watching the video of the injury that Jackson suffered a high ankle sprain.
A high ankle sprain doesn't necessarily mean that Jackson is out of the woods. Remember, Lane Johnson is currently dealing with an ankle injury that still hasn't gone away from last season, and has forced him to miss some games and even come out of games he has started in. We can't really trust whatever timeline the Eagles coaching staff says his injury will keep him out, but I am personally expecting Jackson to miss anywhere from 2-6 weeks with this ankle injury if it is indeed "just" a high ankle sprain.
We all saw how frustrated Jackson was when the injury occurred when he slammed his helmet repeatedly on the turf, so I'd suspect he will rehab as quickly as he possibly can from this to try to get back onto the field.
This is the fifth injury Jackson has suffered since returning to the Eagles (broken finger, sports hernia, reaggrevating said sports hernia, a hamstring issue, and now this ankle injury). He has appeared in just seven games since his return to Philly, playing only ~200 snaps on offense. In those limited amounts of snaps he has 22 receptions for 314 yards and two touchdowns.