The Gunners were forced to substitute Saka, 20, at half-time after he was kicked from behind by the Crystal Palace man while lining up a volley.
Referee Mike Dean had already blown his whistle for an infringement in the penalty area and chose to only book McArthur, who moments earlier had escaped without a yellow card for a cynical foul.
Speaking on Sky Sports, Arteta stated: “We had to take him off because he could not continue, he was very sore.
“I saw the action and I cannot believe how [McArthur] continued on the pitch."
When pressed on whether it was worthy of a red card, he replied: “Absolutely.”
Arteta called on VAR to take a more proactive role in protecting players from the sort of challenge that injured Saka.
He told reporters: “If we want to detect things that are really relevant in a game and can change a football match, then they have to be looked at.
“That situation is not only affecting them but we have to take the player off because of the action so it is affecting it two different ways. It is not right.
“You [need to] make a straight decision, when it is so clear and so obvious straight away and they have to play with ten men.”
The Gunners now face a nervous wait to see if Saka will be fit for Friday’s clash with Aston Villa.
Arteta added: “Obviously he could not continue and he is a boy that is pretty tough and he wants to keep playing, and he could not carry on.
“We have a quick turnaround for the next game, so we will see how he evolves.”
Sky Sports pundits Jamie Carragher and Gary Neville agreed that the Palace midfielder was fortunate, with Arsenal going on to snatch a late 2-2 draw at the Emirates Stadium.
Liverpool legend Carragher noted: “He had a couple of challenges before that, James McArthur, where you said, ‘Could be a yellow’.
“But this is just so strange. Initially you think this is one where they don’t see the player, focusing on the ball and the player comes from nowhere.
“But [Saka]’s actually right in front of him. There’s no way he can’t see him as he is trying to volley it.
“The referee has just blown his whistle, for a handball in the box. He has got away with it. There’s no doubt Palace or McArthur wouldn’t have any qualms if that’s a red card.”