It was a pre-season game. In some ways, that one may have been more impressive. The pass was intended for him, but thrown behind him. The CB that picked it off caught it with a full head of steam heading towards the Patriot's Endzone (it was also caught deep in the opponents territory). Watson had to completely change direction, and still managed to catch the much smaller CB.
I really hope they start using him more as a receiver in the passing game (part of that depends on improving the OL - both he and Graham are needed for blocking a lot, so they're not as available for catching passes).