Manchester United dented Arsenal's title aspirations and won for the third time this week with a 3-2 victory over Arsene Wenger's side.
Here Press Association Sport details five things we learned from the five-goal thriller at Old Trafford.
1. Marcus Rashford has brought the excitement back to Old Trafford.
Remember all those statistics about how shot-shy Manchester United were under Louis van Gaal this term? All they needed to do was get an 18-year-old spearheading the attack. The hosts have scored eight times in the past two home games and Marcus Rashford, a pacy, strong, local lad, has netted half of them to inject some life into his club.
2. Arsenal's inability to win the big game is harming their title bid.
Two defeats to Chelsea, a pair of draws with Liverpool, another with Tottenham at home and this loss, against an injury-hit United squad, could all be pivotal results if Wenger's men do not end up lifting the trophy in May. Leicester must have been delighted to watch them stumble having taken three points themselves on Saturday.
3. Alexis Sanchez's busy summer is taking its toll.
Chile's run to the Copa America title in July meant Sanchez did not enjoy much downtime over the summer. Now, when Arsenal need the ex-Barcelona man the most, he is struggling to replicate his form from last year. He should have relished the challenge of facing Guillermo Varela on Sunday, particularly after the full-back got an early booking, but he was below-par.
4. United's kids are alright.
Rashford will understandably take the plaudits but Van Gaal has introduced a raft of youthful players to senior football recently and most of them have not let him down. Varela had a part to play in the two opening goals here and Timothy Fosu-Mensah looked the part when introduced as a second-half substitute.
5. Van Gaal is not glued to his Old Trafford seat.
One of the most memorable images of Sunday afternoon's clash was seeing United boss Van Gaal leave his seat to emulate what he thought was a dive in front of fourth official Mike Dean. The Old Trafford faithful loved seeing such antics from their boss, who has been much-maligned for remaining rooted in the dugout during difficult times this term.