He didn't even know it existed, at least not until he was bombarded by tweets from fantasy owners in September asking if his injured hamstring would heal in time for the Texans' season opener.
Foster's response -- tweeting an MRI image of the injured leg -- was rooted in logic but proved the 25-year-old was still green in understanding the public's hunger to consume "A. Foster: No. 1 fantasy pick."
"People don't understand this is how I keep my lights on," Foster told NFL.com on Tuesday. "I know I'm in entertainment, but this is how I keep my lights on, this is how I feed my daughter, this is how I make my end's meet.
"I pull my hamstring, and the first thing you hear is, 'Well, are you going to be OK for my fantasy team?' It just kind of struck me as odd that that's the first thing that pops into a person's mind."
At first glance, Foster seems like a laid-back guy -- a belief that gained traction when he was found sleeping on a couch in NFL Network's green room before this interview. He speaks in a soft tone that's contradicted by its assertiveness. Foster has big ideas -- and he cares very much how he's perceived.
Foster is an NFL rushing champion and two-time Pro Bowl pick (he's not playing this year because of a foot injury), but to him, it's more important you know he's a thinker who likes to read and write poetry. It gets to him that he can be lumped into the idea of the "stereotypical football player."
"If somebody sits down to have a conversation with me and really talk to me, they'll go, 'You really seem kind of intelligent for a football player,' " Foster said. "You're just stereotyping, profiling. This is a problem that's been going on in this country for years. I thought we were passed that, but we're not, because I'm their entertainment, and their entertainment isn't usually very intelligent.
"Even people I grew up with that know me, and if I haven't talked to them for awhile, I'll talk to them and I can just hear it in their voice," he added. "They just view me as a football player now, they forget, 'Yo, I'm still Arian that you knew!' It's just ... lame. I can't think of another word, but it just is."
Foster would like to see better publicity for NFL players who do good for their fans and the community. He tries to set a positive example.
"I don't try to do anything proactive. I just be myself," he said. "I've learned you can't change people's opinions. They have to change on their own. So all I can do is be the best example of a human being. It doesn't have anything to do with being a football player. I try not to separate those two. I'm a person. I like to think, I like to read, I like to laugh, I like to cry. It's just you get typecasted so much, you fight stereotypes daily."