United are set to sign the 33-year-old on a free transfer after he left Paris Saint-Germain in the summer.
The Uruguayan has agreed a two-year contract with United and while Neville admits Ole Gunnar Solskjaer needs a new striker, he believes his former club have veered away from their transfer strategy.
‘They need a striker, they need a forward,’ Neville told Sky Sports.
‘I think my emotion when I heard about it yesterday was the feeling I probably had when [Radamel] Falcao signed, when [Zlatan] Ibrahimovic signed, when [Odion] Ighalo signed, it’s very last minute, it’s come up out of nowhere.
‘There is an element of thrill to it, an element of intrigue, excitement, because he’s one of the world’s great strikers over the last five or 10 years.
‘You hope he can come out here and set the stadium and Premier League on fire.
‘There’s also an element of, ‘how have we ended up here?’. Manchester United, two, three months ago, had a great coronavirus period, the club had acted with great class, Marcus Rashford’s work, finished third in the league and you just thought, ‘right, that’s as close as you can get to Manchester City with the team this team they’ve currently got’.
‘They can go and get three or four signings and potentially close the gap this season. And we’re here on the eve of transfer deadline day and nothing’s been done apart from [Donny] Van de Beek who at this moment in time can’t break into a packed midfield.
‘So Cavani tomorrow will be welcome. He’s different than the other strikers. I hope he comes fit and firing, he’s always worked hard, he’s always had a great attitude and work ethic, so I don’t think there’s a doubt around that.
‘I don’t think he’ll come with anything other than to try and prove himself.
‘It’s just a case of I don’t think it was in the strategy, I don’t think it was in the plan, and certainly couldn’t have been because something like this couldn’t have been kept quiet for as long as it has been.’