Sunday 13 March 2016 20:05, UK
It was a dramatic Sunday of FA Cup action, with Watford taking up the third semi-final spot before an entertaining draw at Old Trafford.
Manchester United were saved late on against West Ham by Anthony Martial, but the Gunners failed to take the heat off their manager Arsene Wenger with a 2-1 defeat to Watford at the Emirates.
But what did we learn from the two games? Read on below...
Arsenal miss Koscielny
Not for the first time, Arsenal missed Laurent Koscielny. Odion Ighalo and Troy Deeney have been a handful for most Premier League defences this season, and while Per Mertesacker did a good job of squeezing them in the first half, Watford's first goal after the break epitomised Arsenal's downfalls.
From a throw in on the left, both Mertesacker and Calum Chambers got too tight on Deeney and caught under the ball, before Ighalo was allowed to turn and shoot by Gabriel from eight yards.
The Brazilian's performances in particular since moving to Arsenal from Villarreal last January have been unconvincing. He is nervy in possession and often rash in the challenge, and should have been sent off in the first half for a two-footed lunge on Deeney.
The sooner Koscielny returns from his calf injury the better for Arsenal's title push.
Time up for Wenger?
Winning the FA Cup for a third straight season wouldn't have been enough to appease some of Arsene Wenger's fiercest critics, so a quarter-final exit against Watford constitutes nothing less than a disaster for him.
Chances are that Arsenal will also be out of the Champions League in three days, and could find themselves 11 points off the pace in the Premier League by the time they travel to Goodison Park next Saturday - albeit with a game in hand.
Wenger won't have a cup to hide behind again this season, so failure to catch Leicester in the next two months may finally prove terminal for the Frenchman.
Ighalo's return to form
For nearly 50 minutes it looked like it was going to be another difficult afternoon for Ighalo, whose clinical form in front of goal from 2015 has been largely missing since the turn of the year.
But a first goal in eight games finally came at the Emirates Stadium, as he got onto Deeney's knockdown before turning Gabriel and firing home.
The Nigerian was a handfull throughout, and his delight at scoring was evident as he celebrated just his third strike of 2016, one he will be hoping gets him back on the kind of run that saw him in the mix to finish as the season's top scorer earlier in the campaign.
Fellaini failing to justify a starting spot
It's not very often you'll hear fans cheering when one of their own players gets removed, but that's exactly what happened at Old Trafford when Marouane Fellaini was substituted late on in their draw with West Ham.
With Louis van Gaal's side chasing an equaliser, Fellaini was replaced by Bastian Schweinsteiger with 14 minutes to go - and the home fans were delighted.
Fellaini was equally poor as United were beaten by Liverpool in the Europa League on Thursday night, and with the crucial second leg of that tie to come this week, it is hard to see how Van Gaal can pick the Belgian again.
Boleyn blockbuster beckons
If West Ham go on to end their 36-year wait to win the FA Cup they'll have done it the hard way. The Hammers forced a fourth-round replay with Liverpool after drawing at Anfield and then went on to knock Jurgen Klopp's side out in extra-time in the return at Upton Park.
And they'll have to repeat the feat for a place at Wembley after their draw at Old Trafford. The east Londoners are in the process of saying goodbye to their iconic Boleyn Ground - their home since 1904 - with Stratford's Olympic Stadium their new home from the start of next season.
Victory at the Theatre of Dreams would have put an end to FA Cup football at Upton Park, with the semi-finals taking place at Wembley, so perhaps Anthony Martial's late equaliser was fitting.
The Hammers now have the chance to write a final chapter in the Boleyn's esteemed history on what is due to be an emotionally-charged night at under the floodlights.
Atkinson in the spotlight
Sunday's clash at Old Trafford will be remembered for Dimitri Payet's wondrous free-kick and potentially a turning point for Van Gaal, although that will depend on how United navigate the replay.
But if the Reds do progress into the semi-finals, West Ham will look back on a string on contentious decisions from referee Martin Atkinson which saw them pegged back in the tie.
United had several penalty claims rightfully ignored by the official on Sunday, most notably when Winston Reid's handball went unpunished, however replays showed the New Zealander deflected Ander Herrera's 59th-minute shot onto his arm via his thigh.
The same, however, cannot be said for Hammers' big penalty shout, which came when Marcos Rojo appeared to bring Payet down in the second half.
The visitors were further aggrieved when United's equaliser was allowed to stand, with Bastian Schweinsteiger impeding goalkeeper Darren Randolph moments before Martial's strike found the back of the net.
And West Ham co-chairman David Gold took to Twitter after the game to air his grievances. "Darren Randolph was fouled for the Man Utd goal," he said. "Blatant foul on the magnificent Payet in the penalty area."
