The Spain striker has been linked with summer moves to the Emirates Stadium and Old Trafford.
Morata has a shot saved by Cech
It's fair to say it wasn't the best of starts for the man who scored just 12 goals last season, as the 23-year-old fired an early sitter at Petr Cech's midriff and dragged a second attempt wide of the far post.
Morata's second attempt
Though it's still early doors for Morata at the tournament - and indeed in his career - Red Devils and Gunners alike have been quick to pass judgement on social media.
For the former, the prospect of a 34-year-old Zlatan Ibrahimovic seemed to more greatly appeal, while Arsenal fans appear content with Olivier Giroud - who is already off the mark at the tournament his country is hosting.
It's one in one so far for Arsenal's Giroud
And while the comments weren't all negative, the Morata sympathisers were few and far between...
Today shows why morata isn't worth the money being asked for. He is decent at best.— aman goel (@Xhakalakaboomm) 13 June 2016
Yet some Arsenal fans think he'll be the next time Zlatan "@EmreMeinMan: Morata has scored 25 club goals since 2010 lmao"— 22nd (@Sheezy_AFC) 13 June 2016
Giroud >>> Morata.— DÖ (@khado1096) June 13, 2016
Morata is not better than Giroud's weaker foot...I have said that countless times... £52m for that trash????— Sidney (@sidramatic1) June 13, 2016
I love how all the Arsenal fans waned Morata like a day ago, now they've actually watched him play a game of football they don't— Dylan (@dylanhurley94) June 13, 2016
Given Morata’s performance for Spain today I’m not sure I want him at #MUFC. Probably unfair to judge him based on one match though.— Johan Roelofse (@hunashaman) June 13, 2016
hopefully morata goes to chelsea, fraud of a player— Tom (@T0M123456) June 13, 2016
Morata missed a few good chances today....he will fit in nicely at Arsenal— DJArsenal4 (@DJArsenal4) June 13, 2016
Let Morata be somebody else's project then we'll sign him for £270m in 2020 when he's world class.— London Is Red❄️ (@__LondonIsRed__) June 13, 2016
Giroud did better than this guy
There is no one in this world that can convince me that we should spend £50m on Morata. Dude will not even out score Giroud.— jérémie (@aliladiere) June 13, 2016
Morata would be another Welbeck at Arsenal. Giroud would make him his sideman straight away and bench him— Olly (@Giroudesque) June 13, 2016
Morata is overrated. Giroud,Vardy and anyone with 2 legs>>>>> Morata— Assist Wizard (@ArsenalsCannon) June 13, 2016
United fans have watched Ashley Young play as striker last season and yet this afternoon have decided Morata and Zlatan aren't good enough.— Jack (@JackEC_mufc) June 13, 2016
Staying at Juventus after all?