Arsenal eased to a 3-0 win over Watford on Sunday afternoon thanks to goals from Shkodran Mustafi, Pierre-Emerick Aubameyang and Henrikh Mkhitaryan.Arsene Wenger's side - who stand little chance of finishing in the top four - are now fully focused on the Europa League.They beat AC Milan 2-0 in the first leg of their last 16 tie on Thursday night and host the Italians in the return leg later this week."We have one problem which is Mustafi because he had to come off," said Wenger after the 3-0 win. "It’s a groin problem - I don’t know how bad we have to check tomorrow.""Bellerin is in a good way. He could be available for Thursday. Nacho Monreal as well."Arsenal academy star Reiss Nelson is considered one of the most exciting youngsters at the club but he was an unused substitute in the 3-0 win.Alex Iwobi has been a regular this season but his 18-year-old teammate has found Premier League opportunities hard to come by.

Reiss Nelson's angry reaction on the touchline

Moments after Mkhitaryan made it 3-0 in the 77th minute, Wenger elected to bring Jack Wilshere on as his third substitute.

Nelson, who has only played 18 minutes of Premier League football at Arsenal, was visibly angry at being overlooked by Wenger once again.

According to James Benge, of the London Evening Standard, Nelson was 'fuming' after realising that he wouldn't come off the bench and even "threw his bib to the ground". 

Arsenal fans react

Despite making 14 appearances in all competitions, Nelson still looks some way off breaking into the first team in north London.

The Arsenal fans have high expectations of him and Gooners on social media reacted to Nelson's tantrum on the touchline.

It's strange for an 18-year-old to show such little respect - but you can understand his frustration at watching the likes of Iwobi and Welbeck playing ahead of him.

He'll surely be given a chance in the first team as the season progresses because Arsenal have nothing to play for in the league.

Was Nelson out of line to react so angrily? Let us know what you think by leaving a comment below.