I agree with Flyn, but for some reason that doesn't sound like what Eli has.
I had this same injury my senior year of highschool football. I was a down lineman and my LB rolled up on the back of my legs buckling them, but my cleats stuck in the ground thus all of his weight came down on my foot. It fell, no lies, like I had broke my foot. To get a picture of this take your hand and put your finger tips down on the table and try to bend your fingers backward by pushing down on your finger tips and pushing your elbow forward at the same time.
When I went to the doctor he explained it as its as close to breaking a bone as you can get without breaking or cracking it. Essentially what happens is the muscle on the underneath side of your foot 'stretches out', thus pulling away from the bone. When the muscle contracts it irritates the soft tissue that is a cushion between the muscle and the bone, and thus every time that muscle is stretched or contracted (anytime you walk, run, push off of it, basically anything) it irritates it again. Thats why when you watch the play that Eli injured it, if you watch he goes to push off his back throwing foot (his right foot) but can't and just kind of gives out on it. The doctor gave me 3 options, 1. a Cortisone shot (which I declined because all Cortisone does is masks the pain but creates future damage), 2. Be put in a 'moon boot' (walking boot) and be sidelined for 3-6 weeks at least, or 3. take pain relievers and play through it. It was my senior year so I chose #3, but no matter what pain killers you take its HORRENDOUS pain every time you try to push off with that toe. If this is a legit Planter Fasciitis its much more serious then what most make it out to be. Usually players that have this injury are down for weeks to heal it up.
Again this sounds like a very minute injury, but instead its a very serious injury in terms of harming the players field time and I would not be at all surprised to see Eli sidelined (again depending on the severity of the injury) for a week-weeks. Its not just as easy as 'reducing the swelling' tho, because its not like a sprained ankle, its much more serious than that. Its basically like taking your finger nail and peeling off your finger back towards you, messing with soft tissue can be much more serious then just inflammation. There are different degrees of PF and depending on what Eli has is what the sit out time will be, if the muscles/tendons were pulled completely from the bone it will take many different shots and pain staking hours of rehab and ALOT of rest to cure it. I, again, am no Doctor, but dealing with this identical injury with great severity I know what he went through.
A big thanks to deluxe_247 for the sweet sig!