Spanish striker Dani Lopez, who this time last week was on loan at Barnet, scored a hat-trick and Lucas Akins hit the fourth as the Blades slipped to a first defeat in eight.
Wilson said: "I think we have made all of our mistakes this season in one game.
"Defensively we were second best, we have allowed too much space for all four goals, and they were poor, poor goals.
"Throughout the game I thought we were second best in all areas.
"It shouldn't be a shock because results like this can happen.
"It's how you respond that is the best tonic.
"But in saying that we have got to do better in all areas, there were too many parts of our performance where we weren't competing, where we have been previously.
"I think it's fair to say we're annoyed at how we have lost the game and the way we have performed."