The thing about confidence is that when it's gone, for it to return, it often takes someone else to have confidence in you.
The United manager didn't have to pick Welbeck to replace the injured Robin van Persie.
He could have changed his system or used someone else. After all, Welbeck hadn't scored in the Premier League since the opening day of the season.
A player lacking belief can start doubting himself, second-guessing everything he thought he knew and almost becoming a different player overnight.
Welbeck, still learning at 23 years of age, is one of those players.
But there was a point during the first half at Villa Park that hinted, for now, he's shrugged off some of the inner demons that can affect his performances.
It wasn't his first goal; an instinctive tap-in after Adnan Januzaj's header had come back off the post. It wasn't his second either—another close-range finish after a powerful run into the box.
No, this moment came later; it was a skilful back heel that sent Antonio Valencia thundering into the penalty area.
It was the type of thing you can imagine Welbeck doing all the time on the training pitches at Carrington. It's only occasionally, though, that he tries it on a more public stage. But when he does, it's a sure sign he's feeling confident and playing well.
He did something similar against Swansea on the opening day of the season. Already on the scoresheet in the first-half, he was given another chance in the final minutes. Had he not scored earlier, he might have snatched at the opportunity or tried to hit the target and hope for the best.
As it was, when the ball rolled into his path, he dinked an audacious chip over Michel Vorm and into the net.
It's doubtful he would have even attempted it had he not felt he was already playing well.
Welbeck splits opinion among United fans. He's been accused of not scoring enough goals and not being a "natural finisher."
But he's never really had the chance to shake off those tags.
The records will show that Welbeck's goal return last season was particularly poor. It shows that in 27 Premier League games he scored just once and in 40 games in all competitions he scored only twice.
But the statistics don't offer any context. Sir Alex Ferguson would often bristle at questions about Welbeck's ability to score goals and his answer would usually be in the form of another, rhetorical question. "How often has he played as a striker?"
It's a fair point. With Wayne Rooney and Robin van Persie in the team, there were very few opportunities to play as a centre-forward and his appearances often came on either the right or left of midfield.
Ferguson's point was that you wouldn't criticise Antonio Valencia or Ashley Young for not scoring 15 goals a season so why would you judge Welbeck?
Van Persie's absence is a chance for Welbeck to get a run of games as a centre-forward. It's a chance to see whether he is capable of scoring goals on a regular basis, But more than that, it's a chance to prove the doubters wrong.