Welker himself said it was unintentional. He said he was attempting to go under Aqib, and he figures Aqib was trying to do the same thing. Standard crossing route between 2 receivers that had them cross in such a way to pick the defender. Ideally in a pick, you just disrupt the defender’s route a step or 2 which is a world of difference even in college ball.
Now, if Welker himself says he was running an under route and not a block, then that is something to discuss.
As I said, I don’t think it was an intentionally dirty hit by Welker.
Just two points: First, he saw the ball on the way (he never looked for it again) and secondly, he ran AROUND his own guy.