The Gunners ventured to Old Trafford looking to strengthen their position at the top of the Premier League table after making a positive start to the season.
Mikel Arteta’s men had their moments at the home of the 13-time champions but found themselves a goal down at half-time as Antony marked his Red Devils debut with a goals.
Arsenal were left frustrated by a decision to disallow a goal from Gabriel Martinelli - but those frustrations were somewhat tempered when Bukayo Saka grabbed an equaliser on the hour-mark.
Parity was only in place for six minutes as Marcus Rashford restored the hosts’ lead and the England star confirmed the points for his side went he doubled his tally with quarter of an hour remaining.
Despite the defeat, former Gunners star Merson felt there were positives from the performance for his old club and insisted they will be able to ‘mix it’ with the best this season.
He told Sky Sports: “It’s a 90-minute game, it’s a funny game, football.
“There’s ways of losing matches and I thought, for Arsenal, there’s a lot of positives to take.
“For 60 minutes, bar the opening 10 minutes of the game, for the next 50 minutes, I thought Arsenal dominated it.
“Even when they went one-nil down, they came out in the second-half, it come too easy for them.
“It goes to one-all, the concentration levels, they get caught with a sucker punch and I don’t think they recovered.
“I’m not walking away from Old Trafford thinking same old Arsenal, I’ve seen enough today to show they can mix it.
“I thought they were the better team for most of this game.”
Former Chelsea striker Hasselbaink agreed there were positives for the Gunners but saw deficiencies in their defensive play that will need improved if they are to maintain their challenge at the top end of the Premier League table.
“They (Manchester United) scored the most goals, and it’s all about the goals,” explained the former Holland star.
“Arsenal were good, very good, but you need to be better in the transitions. You come here, they have got speed up front, and they are better without the ball.
“The first ten minutes when they had the ball, they had an opportunity, and they were lucky.
“Overall, they were in control. Yes, Arsenal were good, but you always knew that Man United could counter them and every time they countered them, they looked dangerous.
“It’s all about the goals at the end.”
Arsenal return to action on Thursday night when they travel to Switzerland to take on FC Zurich in their Europa League Group A opener before they entertain Everton in the Premier League on Sunday afternoon.