But what could prove Wenger's final duel with old foe Jose Mourinho ended like so many before it as substitute Fellaini headed home to secure the Portuguese's side victory after former United playmaker Henrikh Mkhitaryan had cancelled out Paul Pogba's opener.

It was a memorable end to a forgettable match at Old Trafford, where the Gunners' hopes of a first point away from the Emirates Stadium in 2018 were scotched at the death.

Arsenal came closer to ending that run than many had expected when the team sheets were handed in, given Wenger made eight changes with an eye on Thursday's crucial Europa League semi-final second leg at Atletico Madrid.

Yet Pogba's 16th-minute opener did not open the floodgates as the visitors produced a performance that belied their many alterations and inexperienced starters.

Mkhitaryan - signed and then sold by Mourinho in January - levelled impressively to become the first player to score for and against United in the same Premier League campaign, only for Fellaini to snatch the hosts a late win that ensures Champions League qualification.

It was a galling way to lose for Wenger on an afternoon that had, at times, felt like his testimonial.

Applauded down the touchline, he was met in the technical area by a warm embrace from Mourinho before Sir Alex Ferguson presented him with a commemorative silver vase.

It was a touching start to a match that started cagily, with neither side managing to muster a shot of note until the 16th minute.

Pogba drove forwards and played the ball wide to Romelu Lukaku. Alexis Sanchez met the striker's cross and saw a close-range header superbly blocked by former team-mate Hector Bellerin, only for the ball to rebound off the post for Pogba to tuck in.

But Arsenal, a side synonymous with a soft underbelly, were not thrown off kilter.

Mkhitaryan hit a low shot just wide of the far post and fellow January acquisition Pierre-Emerick Aubameyang saw a header denied as Arsenal enjoyed a spell in the ascendancy.

Reiss Nelson missed the target as half-time approached - a period United were close to going into further ahead after Ashley Young's cross hit the post after Lukaku was blocked out.

That proved the Belgium striker's last contribution of note as, five minutes after the restart, he was forced off following a kick from Arsenal debutant Konstantinos Mavropanos.

Things quickly got worse for Mourinho's Reds.

Arsenal captain Granit Xhaka capitalised on midfield hesitation to win possession and played across to Mkhitaryan, who darted forward and sent a low drive through Victor Lindelof's legs and into the far corner.

Mourinho was understandably frustrated on the touchline and made changes - just as Wenger did, with another former United man proving a threat as Danny Welbeck took aim from distance after coming off the bench.

Substitute Fellaini sent an attempt over as the hosts stuttered in their bid to find a winner that looked to be beyond them as substitute Marcus Rashford was rightly adjudged offside when bundling in after the Belgian's effort had come off the post.

But what United lack in fluidity they have made up for in spirit this season.

As the match entered stoppage-time, Young floated in a cross and Fellaini directed a header past David Ospina to send Old Trafford wild.

- PA