It doesn’t look provable to me. Could be the Welker attempting to go under the cornerback in the opposite direction.
On this page there are 2 different angles of the hit.
http://nfl.si.com/2014/01/19/aqib-talib-injury-new-england-patriots-wes-welker/
What is very telling is to watch the heads of the 2 bronco’s crossing in the lower frame. Neither were looking for the ball, and that is why it wasn’t caught. Today the receiver is being told to watch the ball and trust wes to take out the dback. ‘take out’ - I dont mean injure, I just mean remove from the play.
Disclaimer. I used to be a Pats fan. I wear a pats coat daily, but it is 20ish years old. I all-but-quit watching the NFL 13+ (or so) years ago when I thought it became to much like pro wrestling. So I never got to enjoy the 3 pats superbowl wins during those years. The pick play was one of the big reasons I quit watching.