Mikel Arteta was left livid after James McArthur avoided a red card after chopping down Bukayo Saka in Crystal Palace's draw at Arsenal.
McArthur made contact with the England international's right leg following a swipe after the latter had cleared the ball away from his own area.
The 34-year-old midfielder was only shown a yellow card by referee Mike Dean for the incident that left Saka clutching his calf on the floor towards the end of the first half of the 2-2 draw at the Emirates Stadium.
But Spanish boss Arteta claimed he could not believe the former Scotland international's caution was not upgraded to a red card, with Saka having to be substituted at half-time following the challenge.