Warrick ended up on IR last year with a shin injury. The shin is still causing him problems, as well as his knee. And he missed practice on Wednesday due to a hamstring problem.
He's a decent player. Certainly a bust. Wouldn't be a bad 5th WR. But right now he's damaged goods.
As a punt returner, he gets a lot of glory, mostly due to his college career. But in five seasons, Warrick's averaged 9.7 yards per return. Welker averaged 10.8 last year. Warrick has 6 career returns over 20 yards. Welker has 7 already. Warrick does have 2 TDs though. But Warrick doesn't return kickoffs, whereas Welker does and can take it to the house.
Welker isn't the fastest or most sudden guy. But he's got outstanding vision and instincts as a return man. He's deceptively effective. And as someone mentioned on the site, he seems to be becoming our Wayne Chrebet this preseason. We'll see if he can continue to improve as a receiver.