McArthur kicked Saka’s calf from behind attempting a relatively unrealistic volley as the Arsenal defence tried to clear the ball on the edge of the box.
The Palace midfielder was cautioned for the incident but was not subject to further punishment from VAR.
The incident left Arteta bemused, with Saka having to be replaced at half-time due to injury.
“Bukayo could not continue,” Arteta said. “We had to take him off at half time. I saw the action and I cant believe how the player (McArthur) continued on the pitch.”
When asked if he thought it was a red card, Arteta added: “Absolutely.”
He continued: “I dont get it. With what we were explained at the start of the season and what happened tonight, it doesnt make any sense.”
Arteta added that he was not sure on the severity of Saka’s injury.
“I dont know, we will see how it evolves,” Arteta said. “Obviously he couldnt continue and hes a boy thats pretty tough and wants to keep playing, but he could not carry on and we have a quick turnaround for the next game, so we will see how he evolves.”
Arsenal had gone ahead early from Pierre-Emerick Aubameyang, before Palace snatched the lead in the second half with goals from Christian Benteke and Odsonne Edouard.
Substitute Alexandra Lacazette, who has been used sparingly this season and has been linked with a move elsewhere, rescued a point for the Gunners with a 95th minute strike.
“Well, we have him! Hes our player, and he shows real commitment so Im not thinking about anything,” Arteta said when asked about Lacazette’s future.
“Im thinking about how to get the best out of him, and tonight he showed a real big moment and how much he cares about the team.”