The 33-year-old scored his second of the game in injury time to give United three points at St Mary’s, in what was a much needed win for the Norwegian.
Cavani had already set-up Bruno Fernandes to get the ball rolling on a comeback but the striker’s half stated auspiciously as he was unable to immediately enter the field for the start of play because of an issue with his boots.
Cavani warmed-up during half-time but he only decided to change his boots just as the second half was resuming, meaning United were down to 10 men for the first moments of the restart.
Solskjaer is perhaps the most famous substitute in Premier League history and though the Norwegian was delighted with Cavani’s impact, he says the Uruguay international must ‘learn’ to always be ready.
Asked about the mix-up, Solskjaer said: ‘He probably wasn’t able to warm up on the pitch [at half-time] but then suddenly he realised he needed bigger studs and I’m happy he did.
‘I don’t know he might have to learn on that one as a sub you always have to be ready. I know more than anyone about that.’
After a dismal start to the campaign, Solskjaer will be hoping that his side have found some form at last.
Paris Saint-Germain take on United at Old Trafford in midweek, where Solskjaer hopes to have Paul Pogba fit to get the point the side need to qualify for the last-16.