They mainly viewed him as returner, it's been said many times. Bevell even said that Lockett surprised him as a WR. Last year showed that they needed a dangerous return-man and they were willing to bet the house on it. Also look at the guys they picked out of other team's practice squad like McCray who was great on special teams. They wanted to improve special teams and figured Lockett was their guy to return punts and kicks, to their surprise he's turned into a pretty good WR too. Also they knew they were going to use him as a WR but they have used him more than Tate in his rookie year, and the thing that stood out to the FO was the way Lockett had alot of scramble drill with his QB in college. If it wasn't for the injury to Lynch and Graham, and our change to a more quick passing game with Wilson, Lockett would of never had been able to showcase his ability as a WR, probably would of only been given less than 35 touches in the season.
Injury has paved ways for many of our depth players to become starters. This has happened for Lane, Maxwell, Sherman, Rawls, etc. Lockett is given the opportunity and he's going to try and run away with it literally.