Edinson Cavani came off the bench to inspire a stunning Manchester United comeback as they turned around a two-goal deficit to secure a superb victory at Southampton.
The 33-year-old Uruguayan striker was a half-time replacement for out-of-sorts Mason Greenwood with Saints two goals up and in control of a fluctuating encounter at St. Mary's - the veteran turning the tide with a virtuoso display and a brilliant headed double.
James Ward-Prowse was United's tormentor in that first half, setting up Jan Bednarek's 23rd minute header with a corner before floating a magnificent free-kick beyond David de Gea 10 minutes later.
Manchester United manager Ole Gunnar Solskjaer, who watched his side waste a host of chances and also had to replace the injured De Gea with Dean Henderson at the interval, sent on Cavani to perform the rescue act and the deadline-day signing obliged in spectacular style.
Cavani was a constant threat, setting up Bruno Fernandes to pull one back just on the hour before showing the old instincts remained fully intact to divert the Portuguese midfield man's deflected shot past the excellent Southampton keeper Alex McCarthy with a diving header, 16 minutes from time.
As the game entered injury time, and with Southampton hanging on desperately for a point, Cavani was the match-winner with a flicked header from Marcus Rashford's cross to spark wild United celebrations as they recorded eight successive top-flight wins away from home for the first time.
Cavani turns the tide for Solskjaer
United had not played particularly badly before Cavani's introduction, they had simply failed to take opportunities that had come their way - Greenwood shooting into the side of an empty net and McCarthy performing heroics within seconds to save from the young striker before recovering brilliantly to block Fernandes.
Once Cavani came on, he was a constant threat and put the previously confident and combative Southampton side on the back foot.
Cavani set up Fernandes to give United a lifeline just before the hour mark, allowing them to play on Southampton's growing nerves and it looked only a matter of time before he hit the target himself with Saints on the retreat as he had a shot deflected over and flashed a header just wide of the far post.
He showed the class that has decorated his career with goals when he pounced to send Fernandes' shot past the defiant McCarthy then provided the final flourish with another deft touch with his head in stoppage time to win it.
It was not a flawless Manchester United performance by any means but being on the road certainly seems to suit them and they showed huge resilience, mixed with quality, for the victory that sends them up into seventh in the Premier League table.
Saints stunned after first-half joy
Southampton manager Ralph Hasenhuttl cut a disconsolate figure at the final whistle after seeing his ambitions of victory turn into hopes for a point before he and his side ended up empty-handed.
How different it was as he urged his side on in a frenetic first half and they responded with the two goals that put them in command.
Saints were never truly comfortable defensively however, relying on the excellence of McCarthy as he added to his fine first-half work to superbly deny Rashford when United stepped up the pace after the break.
The energy and physical power of the first half waned as the visitors took control and even before Fernandes pulled one back there was a sense that the momentum was starting to flow towards Solskjaer's side that a chance taken would only confirm.
Once Fernandes scored, there was only going to be one winner but there was real disappointment for Hasenhuttl and his players, who gave so much but seemed to run out of steam, to have that cruel late blow inflicted.
This still has to be a fine start to the season for Southampton but the defeat will really sting after it seemed like they had Manchester United where they wanted them at half-time.