Sure it was.
Well according the league it was legal. This gif clearly shows that by the time the ball arrives at DT, he puts a lick on Talib. It's a block. Talib should have kept his head on a swivel.
Plus Wes is a little guy. Talib has 4 inches, and 20 lbs on him. He should have demolished through Welker if he wasn't trying to make up lost ground from getting burned on that play.