The Gunners took the lead as a Shkodran Mustafi header was tipped over his own line by the Spaniard.
The lead didn’t last long though as Anthony Martial netted in the 30th minute.
And Savage compared the error to that of Everton star Jordan Pickford in the Merseyside derby against Liverpool.
He said: “David De Gea!
“We had Jordan Pickford at the weekend and now this – he gets two hands on it, Mustafi heads it into the ground on the six yard line and he gets two hands on it and let’s it go through.
“It’s clearly over the line.”
And with United back in the game Savage gave his opinion at half-time.
He explained: “1-1 at half-time. I would say that is a fair reflection, it has not been great quality in midfield for United – do they deserve the equaliser?
“Possibly not. The 3-4-3 formation suits Arsenal better, it looks new to United.
“I think the happier manager at half-time will be Jose Mourinho.”
Arsenal took the lead again in the second half through a scrappy effort but Jesse Lingard hit back immediately once again for United.
Some fans enjoyed De Gea’s error on social media.
One tweeted: “Let’s all slate David de Gea, the same way we did to Pickford.”
Another said: “David de gea doesn’t make mistakes…. He was just doing the Pickford challenge.”
And a third explained: “It was weird to see David De Gea not save that, it was a pretty easy enough save, can’t wait to see what the second half brings, have a feeling Man United or Arsenal are gonna end the match with 10 men..”
De Gea did redeem himself in the second half with a series of magnificent stops from the Arsenal forwards.