Here, Sports Mole takes an in-depth look at whether United were worthy of the victory.
On target: 3
On target: 4
Was the result fair?
If ever a match summed up the 'game of two halves' cliche, this was it. It was on course to be one of the worst in the history of this famous fixture at the halfway stage, with both sides lacking ambition and quality in a terrible opening 45 minutes. United kept the ball better in that first half, but their possession was slow and rarely threatened Liverpool's goal, with the hosts' best moments coming courtesy of defensive errors from the visitors. Liverpool, meanwhile, had even less to shout about.
The game was screaming out for a goal, and Blind provided with a moment of quality that had been severely lacking up to that point. The second half was almost unrecognisable to the first, with both sides beginning to show a little more intent going forward. Herrera's penalty threatened to put the game beyond Liverpool, but Benteke's magnificent bicycle kick six minutes from time looked like it had set up a grandstand finish. However, Martial ensured that his debut would be a memorable one with a fine goal shortly afterwards that showed exactly why he has been compared to Thierry Henry.
United only had the three shots on target today, but they scored with all of them and there is little doubt that they warranted the three points here. It was by no means a vintage performance from the Red Devils, and they can't expect to win too many games against the big boys playing like this, but they were still the better side on the day. Liverpool offered very little in response and can have no complaints whatsoever at leaving Old Trafford empty handed once again.
Man Utd's performance
It has been a strange time for United over the international break. The David de Gea saga and Martial signing dominated the final days of the transfer window, and Louis van Gaal would have been looking forward to just getting back to playing football today. De Gea was handed his first start of the season, but Martial was forced to begin the game on the bench, despite the absence of Wayne Rooney through injury. The youngster may have been able to make an impact in the first half, with United's main problem being their lack of pace in the final third with Marouane Fellaini as their striker.
It was a dull and uninspiring first-half display from the hosts, despite them keeping the ball nicely for long spells. They lacked any real cutting edge, but showed some creativity at the start of the second half with a well-worked free kick routine that provided the opening goal. That sparked them into life, and suddenly there was an injection of pace into their attacks. They began to look a great deal more threatening going forward, while at the other end of the pitch they were rarely troubled.
Having said that, Blind was forced to clear one off the line, and there was nothing they could do about Benteke's stunning strike to halve the deficit. Van Gaal will be delighted with how his side responded to that, and the fact that it was Martial who got the goal - in some style too - will only add to the celebratory feel for the hosts after this match. It was by no means perfect, but any victory over Liverpool is special for United and they will now look to use this as a springboard to kickstart their season from.
After such a disappointing result before the international break, Brendan Rodgers would have been looking for a response from his players today. Simply put, he didn't get one. The first half was one of the worst 45 minutes of football for a long time, but United at least managed to keep the ball fairly well. Liverpool gave it away time after time, often in dangerous areas. It was a performance littered with defensive errors and void of any attacking threat at the other end of the pitch, with Benteke woefully isolated.
Rodgers's tactics must be questioned, with Danny Ings operating in a wider role that clearly didn't suit his game, while Roberto Firmino was also played out of position. Those tactics stayed the same from start to finish, with Rodgers failing to change things even when his side were chasing the game. They did at least improve in the second half, but it was only when they fell behind that they started to show any sort of ambition. They did have their moments after the break, but ultimately they did nowhere near enough to get something out of this game.
A number of players all over the pitch had poor games, but perhaps the most worrying thing from a Liverpool perspective was the lack of fight in the team. United are still considered by most to be Liverpool's biggest game of the season, but there was nowhere near as much passion on show today as there has been in years gone by. There were far more negatives than positives for Liverpool today, and the pressure is already beginning to build on Rodgers.
Sports Mole's man of the match
Daley Blind: His defensive shortcomings were questioned after the recent defeat to Swansea, but Blind excelled at the back today. He helped to keep Benteke very quiet, while also popping up with huge contributions at either end of the field. His goal was very well taken, and he cleared one off the line brilliantly later in the second half.
Take your pick. Liverpool had a number of defensive mistakes in the first half, but the most costly of the lot over the course of the match was Joe Gomez's tackle on Herrera to concede a penalty. The youngster has impressed since his summer move, but he showed a bit of inexperience when going to ground and Michael Oliver had little choice but to point to the spot.
Oliver may have been expecting a tougher assignment from a fixture that has produced 16 red cards in the Premier League era - second only to the Merseyside derby. He only really had to make one major decision, and that was the correct call in awarding United a penalty.
Man Utd: United make their return to the Champions League proper on Tuesday night, taking on PSV in Eindhoven.
Liverpool: Liverpool are also in European action as they travel to face Bordeaux in the Europa League.