Meanwhile, Liverpool drew yet another match, their inferior quality from the bench – and Jurgen Klopp’s hesitant tactical decisions – costing them the three points at Goodison Park.
But what did we learn from the weekend's action?
Solskjaer again proves more than just a motivator
As the weeks go by it is increasingly difficult to ignore Ole Gunnar Solskjaer’s tactical acumen at Old Trafford.
Despite numerous injuries to first-team players, Manchester United came back from behind to beat Southampton on Saturday courtesy of Solskjaer’s formation switch in the second half, moving from a diamond 4-4-2 to a 3-5-2 when Alexis Sanchez was replaced by Diogo Dalot in the 52nd minute.
Ashley Young played well as a right-sided centre-back, allowing United’s midfielders to push higher up the pitch, safe in the knowledge that Southampton’s counterattacks would be controlled by a three-man defence.
The switch mostly benefitted Andreas Pereira, who moved into the number 10 role behind Romelu Lukaku and Marcus Rashford; Pereira scored United’s first then set up the second from this adjusted position.
United used six academy products over the course of the 90 minutes, while Lukaku’s form notably improved and the team found a way of creating chances even without Paul Pogba playing particularly well. Solskjaer can do no wrong.
PIC: Pereira touches vs Southampton
Emery exposes Spurs' shortcomings
Arsenal’s assured defensive performance at Wembley Stadium on Saturday was arguably their most impressive on the road this season, with Unai Emery deploying a more conservative approach than usual to keep Tottenham quiet.
Not only did Arsenal only press in short phases, inviting Spurs onto them, Emery also instructed Shkodran Mustafi and Nacho Monreal to remain in line with the centre-backs at all times.
The Spurs wing-backs struggled to get into the game as a result, Mustafi keeping Danny Rose in his pocket as the hosts showed an inability to play with tempo through the centre of the pitch.
Mauricio Pochettino’s side resorted to long balls forward because the Arsenal midfield was packed with bodies and the wing-backs were isolated; Arsenal’s humble defensive approach was the right way to expose Spurs’ laboured build-up play over the last couple of weeks.
Pochettino's panicking almost costs Spurs
The more interesting tactical aspect of the North London Derby, however, was Pochettino’s unusual second-half substitutions.
He replaced Victor Wanyama with Erik Lamela in search of the three points, dropping Christian Eriksen into a deep midfield role. From here, the Denmark international was able to get on the ball more frequently – he created a chance within moments of the switch – but was also a liability defensively.
Granit Xhaka dribbled past him and straight through the Spurs midfield a few minutes later, prompting Pochettino to make another alteration.
Fernando Llorente came on for Son Heung-Min and Spurs moved to a gung-ho 4-2-4, with Danny Rose in central midfield alongside Moussa Sissoko. Rose was predictably erratic in this unfamiliar position, playing wayward passes and generally lurching out of position throughout the final 10 minutes.
The switch also meant Spurs were far too attacking generally, leaving huge spaces on the flanks, allowing Henrikh Mkhitaryan to beat just one player before putting Pierre-Emerick Aubameyang through on goal.
Arsenal earned a penalty and, had they scored it, Pochettino would have been at fault for those bizarre tactical changes.
PIC: Rose passes vs Arsenal
Klopp's lack of killer instinct again limits Liverpool
Liverpool have now drawn five of their last seven matches in all competitions, reflecting the difficulty they are having breaking down opponents that have learned to sit deep and double up on Sadio Mane and Mohamed Salah.
There simply is not enough creative guile in the Liverpool midfield, meaning the front three are comfortably thwarted when space in behind is limited.
But Jurgen Klopp could have made braver substitutions at Goodison Park, and indeed his emerging cautiousness could be the difference in the title race; Liverpool need to be more daring, to take greater risks, if they are to overtake Man City.
On Sunday, Klopp made three like-for-like substitutions, maintaining the same 4-3-3 shape throughout even though it was not working.
He could have started Xherdan Shaqiri in a 4-2-3-1 considering how poor Everton’s defensive record is this season, and certainly Klopp should have tried a more attacking system at some point during the match.
Instead, he betrayed his own nervousness by refusing to gamble.
Fulham frailties highlight technical deficiencies
Scott Parker’s first game in charge of Fulham ended in defeat, and although he endeared himself to the crowd by reinstating Tom Cairney in his preferred No.10 role, this match was a stark reminder that Claudio Ranieri was not the problem at Craven Cottage.
They simply do not have enough quality in key areas of the pitch.
Denis Odoi and Havard Nordtveit continued their poor form by losing Gonzalo Higuain as he made space to score the opener, turning in a cross that came via a very simple overlapping run on Chelsea’s right.
Ryan Sessegnon was unable to track back in time and Kevin McDonald did not spot the danger and help his left-back – as usual.
The second goal was equally chaotic, Odoi failing to prevent Eden Hazard from cutting inside before Fulham dropped far too deep, giving Jorginho space to find the top corner.
It does not matter who is in charge of Fulham; they don’t have enough quality for this level.