As plenty have already pointed out, Campbell had a great first season and showed all the attributes of a very good striker with strength, speed, link up play and most importantly a decent work ethic.
Last season, he joined everyone in out poor start and never really looked like trying to get back to how he was. He was lethargic, appearing lacking in effort and interest and for the most part, was a waste of a shirt.
Hopefully Wilder has given him the kick up the arse that he needs, by putting him on a separate training plan, highlighting that he needed to put extra effort in to get back to an expected level of fitness.
If he can get anywhere near what he was in the first season, he will be a real asset.
I would like to see if a Campbell/Bamford pairing would work. If they can get a good understanding of each other then they would cause all sorts of problems. But only if Campbell knuckles down and shows some effort.