DI MARIA HAD TO GO, BUT MONREAL WAS LUCKYIf Angel di Maria had played to the whistle, he would've ended the game on the pitch. Yes, there was a slight tug from Nacho Monreal and on the continent he'd every right to go down, but if he'd left the decision up to ref Michael Oliver, then the farce that led to his dismissal would've been avoided. You can't put your hands on the ref, even if Di Maria was acting in frustration rather than ugly aggression. What was strange was Oliver didn't confirm it was Di Maria who grabbed at his back with his assistant. It appeared he relied on the word of protesting Arsenal players. Among them was Monreal, who also put his hand on Oliver's shoulder after Di Maria's actions. It wasn't as demonstrative as the Argentine, but the Spaniard was fortunate that everyone missed it - including the TV.

UNITED KICKED OFF LIKE THEY WERE IN EASTERN EUROPEIn the days of Sir Alex Ferguson, any big game at Old Trafford would kick off with Manchester United on the front foot. The first tackle would be a screamer, the wide players would be flying and the ball fizzing across the pitch. But last night, United handed the opening exchanges to Arsenal. The ball, when under United's control, went sideways and backwards. It was like they were kicking off away in Eastern Europe, not at home in an FA Cup tie against one of their greatest rivals. That Alexis Sanchez carved out the opening chance was no surprise.

DI MARIA NEVER SKINNED ANYONEThe manner of Arsenal's opener, inspired by a superb run from Alex Oxlade-Chamberlain, is what United are seeking from Angel Di Maria. But sitting on the right-side of United's midfield, the Argie NEVER found a way outside of Nacho Monreal. The goal, created for Wayne Rooney, even came from Di Maria checking back before delivering a terrific cross for the captain to head home. But it was more about Monreal, who appeared to be still basking in the spotlight of his goal, not getting tight on the No7 rather than flashy piece of skill. Di Maria had so much time, it was almost a dead-ball moment! The winger never skinned a player during the 77 minutes he was on the pitch. United's midfield didn't help. Just as he failed to beat Monreal on his outside, there was no passing through the lines for Di Maria to rush onto.

WENGER ENCOURAGES INDIVIDUAL SKILLThe contrast in attitude of the two managers was most stark in midfield. Arsenal's players, obviously encouraged by Arsene Wenger, were always happy and confident enough to back their skill to beat their immediate opponent. Time and again, Mesut Ozil, Santi Cazorla and even Francis Coquelin would drop a shoulder and go past a United tackler. In Red, the midfield's first reaction was to get rid of the ball, sideways, backwards, especially in the opening half-hour. United eventually threw off Louis van Gaal's shackles in the final 15 minutes and finished the half, with the scores locked at 1-1, the better team.

LVG HALFTIME CHANGES STUNNINGAt the break the momentum was definitely with United. Then Van Gaal made his changes. It was stunning. The final 20 minutes of that first-half was a thriller. But LVG pulled off Ander Herrera and Luke Shaw to replace them with Michael Carrick and Phil Jones. Sticking two holding midfielders (Carrick and Daley Blind) in front of a back four simply invited Arsenal to play more in United's half. It was staggering, given it was a Cup tie - you play to win - United were at home and had gone into the locker room the better team. Van Gaal afterwards declared the loss "self-inflicted". Yes, it was, Louis.

WELBECK DESERVES TO CELEBRATE WINNERPer Mertesacker told us in the post-match that Danny Welbeck was "quiet" in the away dressing room afterwards. But he wasn't so quiet after sweeping home the winner. United fans shouldn't complain with Welbeck's reaction, he never put in for a transfer, it was Van Gaal's decision to sell. It can't be argued Welbeck had a great game, however. It was a clumsy, awkward performance from a player now second fiddle to Olivier Giroud. However, he can be well pleased with his revenge on LVG. But why was Phil Jones chesting the ball down to Antonio Valencia in such a dangerous area of the pitch? Even if the Ecuadorian's back pass had been clean, it still would've been a risky piece of play. Would Jaap Stam or Steve Bruce have done something similar?

WHAT CAN FALCAO DO?Staggering, absolutely staggering. United are chasing a goal and LVG goes with Adnan Januzaj ahead of Radamel Falcao for the final 20 minutes. Only a week ago, the Dutchman was complaining none of his strikers were capable of scoring "20 goals". Well, it's bloody hard to do so from the United dugout! It's great that Marouane Fellaini is proving his value this season, but he shouldn't be United's best performer in games like this. The Belgian was United's key attacking outlet, with Rooney leading the line ahead of him. If Falcao had been thrown on, Rooney would've been on the ball more playing deeper. And you still don't lose the effectiveness of Fellaini in the air. Even with Januzaj on, LVG insisted the left-footed winger play on the right!

ARSENAL DESERVED THE WINIn the end, Arsenal deserved their triumph. It wasn't a classic performance from the Gunners, with many of the night's performers going into the game short of confidence. But when you have Alexis and Cazorla in their current mood, you're always a chance. Wojciech Szczesny, bar Rooney's header, never had a serious save to make, though he also was shaky at crosses. Mertesacker, hammered for the defeat to AS Monaco, grew in confidence as the game rolled on and it was the big German who produced the final decisive moment of the Cup tie when he blocked Chris Smalling's last minute effort.