The title race has been blown wide open by Manchester United's brilliantly orchestrated 2-0 victory over Chelsea at Old Trafford, after Tottenham Hotspur's accomplished 4-0 win on Saturday highlighted why they, and not Antonio Conte's side, are the most interesting team in the Premier League.
Incredibly, none of the bottom nine teams recorded a win on what was an underwhelming weekend in the lower reaches of the division.
Here are three tactical things we learnt from the Premier League action:
1) Several of Chelsea's upcoming opponents will benefit from Mourinho's discovery of a new way to defeat Conte's team
To a man, United were superb on Sunday afternoon.
Aside from winning the individual battles and the Yorke-and-Cole style striker partnership up front (see below), it was their 4-4-2 shape that suffocated Chelsea into submission.
Mourinho's team constantly attempted long balls over the top of the defence (76 in total), which – coupled with the aggressive wing-play of Ashley Young and Antonio Valencia – forced Chelsea into a fearful and retreating flat back five. Consequently, N'Golo Kante and Nemanja Matic had an enormous area of the pitch to cover single-handedly (Pedro and Eden Hazard, who was brilliantly marked out of the game by Ander Herrera, stayed too high and thus isolated their midfield team-mates).
Having successfully chopped Chelsea into three disjointed parts, Marouane Fellaini and Paul Pogba used their physical strength to dominate Conte's midfielders – something helped by those constant long balls up into midfield.
The strong midfield, aggressive full-backs, man-marking of Hazard, and long balls over the top culminated in United winning all the second balls and overwhelming the visitors.
2) Hughes discovers why the narrow 3-4-2-1 has taken over English football
Conte's 3-4-2-1 may not have worked at Old Trafford on Sunday, but on the whole, it has come to dominate English football in 2016/17.
Stoke City are the latest team to learn its advantages, after Mark Hughes finally embraced the system for his side's 3-1 victory over Hull.
Having tentatively tested the central-playmaker-heavy system at Burnley a fortnight ago (but with the defensive Joe Allen in attacking midfield), Hughes was braver on Saturday.
Xherdan Shaqiri and Marko Arnautovic worked well together in central areas, benefitting just as Hazard and Pedro have under Conte.
Like the two Chelsea attackers, Arnautovic and Shaqiri love to float in the middle even when instructed to start out wide - and rarely track back.
Allowing two playmakers to stay in the opposition half throughout the match is arguably the biggest advantage of the 3-4-2-1.
Arnautovic's opener and Shaqiri's clincher were the result of Stoke storming through the middle, and on both occasions one playmaker assisted for the other. Hughes will, no doubt, try this tactic again over the remaining five matches.
3) Rashford's brilliance suggests United have a high-tempo future without Ibrahimovic
There isn't much about Mourinho's tactical strategy on Sunday that can be reused long-term, largely because it was a defensive system designed to stifle, not create.
But the Rashford and Jesse Lingard partnership should become their template for the 2017/18 season; along with Antoine Griezmann, they could create one of the quickest, and most exciting, attacks in the country.
Rashford's strength up against David Luiz was the biggest surprise of the weekend. His tireless running and excellent hold-up play helped take United higher up the pitch, providing a considerably more mobile fulcrum than Zlatan Ibrahimovic has managed since joining the club.
The Swede has overall been a hindrance to the club, with his goals masking a negative influence; Mourinho will not shake off the low tempo, safety-first attitude with a 35-year-old roaming up top.
Lingard is a very underrated footballer; in a more aggressive shape-shifting side than that presided over by Louis Van Gaal or Mourinho, the 24-year-old would have become one of the country's most exciting playmakers by now.
His intelligent interplay with Rashford proved as much – and taught the United fans that these two academy products can bring the good times back to Old Trafford.
Best of the Work – Guardiola's tactical switch to crowd out Saints
Many would have groaned when the Manchester City line-up was announced.
Against such a narrow, central-midfield-focused team as Southampton, it appeared odd to leave Raheem Sterling out of the side. Pep Guardiola has found a lot of joy in recent weeks by instructing his two quick wingers, Sterling and Leroy Sane, to hug the touchline, which looked like a good tactic to get around that congested Saints midfield.
Instead, he employed Kevin de Bruyne on the right in an attempt to win a straight-forward possession battle in central areas. After a very stodgy first half, his plan began to work; De Bruyne increasingly found pockets of space in the inside-right space, eventually creating two goals for his team-mates.
Worst of the week – Bournemouth
Eddie Howe will never improve his appalling record against top-six clubs until he takes a braver tactical approach. Bournemouth sat very deep at White Hart Lane, allowing Pochettino's defenders as much time as they wanted and sitting in three flat lines (in a 4-4-2).
As a result of being non-confrontational and sitting in rigidly straight lines, they found it very difficult to track the movements of Dele Alli, Harry Kane, and Christian Eriksen.
Given all the time in the world to pick their pass, Spurs' centre-backs waited until Alli or Eriksen jinked between the lines before slipping the ball into the final third. Anything other than a high-pressing approach will always fail against Tottenham – the most positionally intelligent and tactically malleable team in England.