I don't see how Marshall is a great YAC threat. I mean he had a 4.2 YAC average last year. Welker had 6.8, for a total of 754 YAC yards. Marshall had 436 total YAC. Leave it alone, Marshall is a deep threat and a good WR who I think is good at YAC, but Orton will have trouble getting Marshall the deep shots, guaranteed. Orton having low arm strength isn't going to do Marshall any favors. It's going to be tougher to get Marshall the ball if defenses know he's running shorter routes all year.
You dont see because you dont watch him play. Marshall is a huge threat after the catch, just watch him as opposing dbs and lbs attempt to attack him. He is elusive, has good vision for a wideout, and runs with power. Hes 6'4 210+ making him a big guy to bring down. Just because he doesnt have the numbers doesnt mean anything.
And you have to think about this. Welker has a shitload of plays designed for him to make a play after the catch. The guy runs more bubble screens than just about anyone in the league. Marshall on the other hand is a more complete receiver as his route tree is more complete. He is asked to run routes short, intermediate, and deep, while welker on the other hand is running short routes more often than not. Because of that, he has more chances to create plays after the catch because when he catches the ball, many people arent around him. And he plays in the slot, so must of the time he isnt covered head up, or is covered by a lb...who cant run with him, thus creating yac oppurtunities. At the end of the day, Marshall is WAY better than welker after the catch. Welker is solid, but his main assets after the catch is his quickness...thats about it. And marshall isnt a deep threat. He doesnt have the speed to stretch the field consistently. His deep shots usually come off of double moves, or errors in coverages. Marshall never was known as a guy who was a deep threat ala randy or fitz. Not his game, he only had 1 catch last year that was 40+ yards...thats not a deep threat. Watch him play more often and see for yourself.
[media]http://www.youtube.com/watch?v=16qhwX26vOA[/media]
And many people dont know this but marshall drops a shitload of passes. I believe last year he dropped like 12-15 passes. If he could become more consistent as far as his hands, he would have way more catches, and better numbers.