He should know where the first down is, but it's not like he has the yellow line in front of him like we see on TV. He just wanted to be sure he got it. But yeah, he should've slid.
Anyone else see his hand clench after the hit? That could be a big issue, neurologically. He really should retire. I like the guy, but I don't want to see him regret it in like twenty years if he keeps going on this way.