X-and-O Flashback: How Welker makes Patriots offense go (2009)
This is an article from a couple years back but if you love x’s and o’s like me it’s well worth the read.
One thing you’ll notice from the video is how adroitly Welker adjusts the nature of his route to the coverage he faces. Against tight man coverage, he might jab-step and juke a defender and make a flat cut to get open, while against loose man coverage or a softer zone he might “speed cut” the route — i.e. roll the cut in a way that is not quite as precise but where he doesn’t lose speed as he changes direction.