That’s three league wins on the bounce for United then, and it hoists them firmly – for the moment at least – into the top six race once again.
Southampton will rue the missed chance here – at 2-0 up, after that Ward-Prowse first-half performance, they should have been home and dry – but they will surely learn from this cruel late loss.
A clean sheet for Dean Henderson on his first Premier League game for Manchester United, brought on after David de Gea’s injury.
But it is Cavani, the late-window buy who brought his years of experience to bear after he replaced Mason Greenwood.
Ole Gunnar Solskjaer was outfoxed in the first half but he has trumped Ralph Hasenhuttl at the final post here.
Edinson Cavani brings Manchester Untied back from the brink at St Mary’s Stadium – and then some! – as the Red Devils snatch a dramatic late win against Southampton in the Premier League.
Jan Bednarek and James Ward-Prowse had put Southampton on course for a stellar win.
But Bruno Fernandes rolled United back into it before Cavani’s headed double snatched the points.
The visitors preserve their perfect away record in the top-tier this term after the Uruguayan’s brace of headers and assist – and their hosts slump to a first defeat in eight games.
United should have been ahead in the seventh minute when Alex Telles played Mason Greenwood through after poor defending from Jannik Vestergaard, however, the striker could only hit the side-netting after rounding McCarthy.
The visitors were in the ascendancy early on but went behind against the run of play as Bednarek glanced home an excellent corner to the near-post from Ward-Prowse.
Kyle Walker-Peters then saw an effort deflected onto the left-hand post before McCarthy atoned for his own error to prevent Fernandes from finding an equaliser.
Another pinpoint set-piece from Ward-Prowse punished United for their failure to take that chance to restore parity, his ninth goal from a direct free-kick in the Premier League squeaking inside the near-post despite David de Gea getting a hand to it.
De Gea then denied Moussa Djenepo after a quick break but received treatment having appeared to injure himself when he clattered into the post in a vain attempt to keep out Ward-Prowse’s free-kick and was eventually replaced by Dean Henderson after half-time.
Cavani also entered the fray and had the desired impact as he picked out Fernandes to convert on the turn.
Fifteen minutes later Cavani levelled matters with a show of clinical finishing that he repeated in injury time as he stooped to head home Rashford’s delivery and send United seventh in the table.