The match descended into a scrappier contest, with Arsenal losing Rob Holding and Aaron Ramsey to injury, as both sides seemed to struggle with the torrential rain and slick surface.
Martial levelled four minutes later, sweeping home after Marcos Rojo's free kick was well-saved by keeper Bernd Leno but Herrera, who had looked offside, kept the ball alive and squared for the Frenchman. "The 15 minutes he was on the pitch he played well, in a moment where our defenders couldn't push up".
Should de Gea be dropped?
Aubameyang was denied again by a sprawling De Gea and Jose Mourinho threw on Paul Pogba, but neither side could find a victor, with United's goalkeeper making a fine late stop to prevent Lucas Torreira from snatching victory. But the two goals they scored were flukes, David de Gea should never palm the first into his own goal, and the second was even luckier.
What does it mean? Their unbeaten run stands at 20 matches in all competitions.
Man who ran over Charlottesville protester guilty of murder
Wednesday, fellow protesters testified that Fields asked them to lunch shortly before ramming his auto into a throng of people. Calhoun testified that Fields was calm and seemed exhausted . "I thought they were attacking me".
Claudio Ranieri's side are rock bottom of the Premier League table despite picking up a point against Leicester on Wednesday but the Portuguese full-back has already learned there are no easy games for United, who have not won any of their last four league matches.
Manchester United's Marcus Rashford believes Arsenal have become one of the Premier League's strongest teams again under Unai Emery ahead of their trip to Old Trafford.
The 25-year-old established himself as a key player for club and country last season as Jose Mourinho's men finished Premier League and FA Cup runners-up, before helping England reach the World Cup semi-finals. We're just trying to get better game by game.
United's defence has been their main problem so far this season, and whilst they still conceded two goals against Arsenal, they looked a lot better with Bailly at the back.
Former France defender Laurent Koscielny could come into the matchday squad, after twice playing for Arsenal Under-23s, either on Saturday or next week against Qarabag in the Europa League.