Former United skipper Bruce knows the standards required to be a regular at Old Trafford and fully expected Welbeck to reach them.
Bruce said: "I'm not surprised at the impact he has had at United because, for someone so young, some of the things he did for us were terrific.
"We saw while he was here what a top, top player he is. I think Sunderland was great for him and he was great for us. Sir Alex said all along that Danny would only be with us for a year.
"There was no chance that we could keep him - certainly not after his performance in the 3-0 win at Chelsea!
"So it wasn't even worth asking the question in the summer. I'd have loved to have kept him, even on loan, but it was never an option."