Arsenal consider UEFA complaint against Atletico Madrid following Champions League game

Atletico then watered the pitch at halftime, dousing the end Arsenal were defending with more water than the other. There are strict UEFA regulations on the condition of the pitch, which state "the home club must make every reasonable effort to ensure that the pitch is in the best possible condition," and they will undergo strict pre-match inspections.

UEFA's Article 34 also states: "The home club must respect the pitch-cutting guidelines for natural grass pitches. The height of the grass must not exceed 30mm and the entire playing surface must be cut to the same height.

"The height of the grass should be the same for both the training sessions and the match. If deemed necessary by the referee or the UEFA match delegate, the home club may be required to reduce the height of the grass for the match and training sessions.

"The pitch-watering schedule must be communicated by the home club at the organisational meeting. The pitch must be watered evenly and not only in certain areas.

"As a general rule, pitch watering must finish 60 minutes before kick-off. However, upon the decision of the home club, pitch watering may also take place after that time: between 10 and 5 minutes before kick-off; and/or during half-time, for a maximum of 5 minutes."

UEFA has been collecting evidence and investigating the matter, though it remains unclear whether Arsenal will pursue it further.

Meanwhile, Diego Simeone's behavior on the touchline as officials reviewed VAR footage surrounding referee Danny Makkelie's decision to reverse a penalty call could potentially land him in hot water.

That outcome would hinge on the fourth official flagging the issue to the referee and subsequently including it in his match report. UEFA may seek feedback from the VAR team following Makkelie's decision to review the screen footage 13 times before reversing his original call.

That contradicts VAR's mandate to intervene only in obvious mistakes, but Mikel Arteta's post-match grievances have likely achieved their objective before the return fixture. Gunners midfielder Declan Rice suggested on television that the official might have been swayed by the home supporters and, while that could suggest partiality under Premier League regulations, it would be highly unusual for UEFA to intervene.