Will it be Manchester United or West Ham United who go through to the Wembley semi final? We're still no closer to finding out. The craving to decry Manchester United's fall from grace at the top of English football on the back of this - and many other - games must be tempered by the rise towards the top of this fabulous Hammers side. But the temptation is to point out that Manchester United fans are reasonably happy with a late equaliser to set up an FA Cup replay at Upton Park. Hardly the aura that the Manchester United of old had. From a Hammers point of view, refereeing mistakes perhaps cost them victory, but Upton Park will host one last FA Cup game, and it could be a game to send West Ham to Wembley - what a dream that would be.

Despite a cagey first 45 minutes, the second half sprung into life and featured end to end football in the vein of a proper cup tie. With 15 minutes remaining, man of the moment Dimitri Payet produced a spark of brilliance from a free kick to give Slaven Blic's men the lead before United's young French forward Anthony Martial levelled with a volley from inside the box to force the replay.

We can point to a couple of calls made by the referee and things that went against West Ham, though on the balance of play a draw was perhaps a fair result, and after all, it does set up that mouth-watering replay!

Here are the five things we learned from the game:

Emenike needs more practice on the training field

Although it was a scrappy first half, West Ham's on loan forward Emanuel Emenike managed to spurn two good opportunities to put the Hammers in front even within 20 minutes. Bearing in mind he bagged a brace in his first start in a West Ham shirt against Blackburn Rovers in a resounding 5-1 win in the previous round of the FA Cup, the former Fenerbache attacker needs to put more work in on the training ground. There's no doubting that he's what the Hammers could be doing with up front, but he has to show a little more between now and the end of the season.

Where is Fellaini's best position?

At 6"4 Fellaini is surely a player Manchester United could use in a more positive and effective way. The former Everton midfielder was playing alongside Michael Carrick in the defensive midfield position where the Belgian has lacked creativity in the past. He is seen as more of an attacking midfielder, and Van Gaal has, in the past, used Fellaini to good effect as a domineering striker.

Putting his height to better use might have been a better tactic in an FA Cup tie where both teams were going hammer and tongs in the second half, but Fellaini failed to please the home faithful and was ultimately taken off and replaced by the returning Bastian Schweinsteiger to perhaps the biggest applause of the afternoon.

Carroll is improving

West Ham manager Slaven Bilic preferred formation is a 4-2-3-1 with striker Andy Carroll playing as the lone striker. However, this afternoon saw him  partner Emenike. This could be very effective in the future as Carroll's work ethic in chasing down the likes of David De Gea, Chris Smalling and Marcos Rojo put the Red Devils under pressure.

The former Liverpool and Newcastle United forward walked out of Old Trafford unscathed, which is a big plus for the England man. If he can stay fit for the remainder of the season then West Ham's hopes of a place in next season's Champions League could become a reality.

Lack of centre back options for the Hammers hurting

Prior to this thrilling encounter, the East Londoners were lacking in centre back options. Despite Winston Reid returning at the heart of the defence after a month out with a hamstring injury, the New Zealand international was not fully fit, while James Tomkins and James Collins were never going to make the starting XI.

Ultimately, this is why West Ham will have to go through all of this again, as Martial's leveller could be stopped as the Hammers will have to wait a little longer in order to book their place at Wembley.

Dimitri Payet - signing of the season?

Over the course of this season, the Premier League has been treated with the brilliance of midfield playmaker Dimitri Payet. His skill and flair is an absolute joy to watch and in today's tie his goal tally increased to 11 for the season. It's entirely possible that Payet is the man who will almost-singlehandedly bring Champions League football to East London next season.

His superb free kick today left De Gea rooted to his line as the Hammers fans went into delirium and sung his name throughout. Quite possibly, Payet is the signing of the season in the Premier League.