Athletic Bilbao and Chivas Guadalajara will play the first edition of the Tree of Gernika Trophy on Sunday.

This will be the first leg of a special new symbolic tournament with a unique format. The tournament will be played over two legs - one game in Spain, the return leg in Mexico next summer but unlike traditional two-legged cup ties, the aggregate score over the two games will not count and nor will goal difference or away goals.

Instead, the tournament will be decided by a penalty shoot-out (five per team then sudden death), regardless of the outcome in each leg.

Another curious feature is that both teams will be allowed unlimited substitutions - as long as all of the changes are made within a maximum of three windows. So everyone will have the chance to play.

Sunday's inaugural game will be played in Bilbao at San Mamés with the return leg taking place with Chivas hosting Athletic at Estadio Akron in Zapopan, Mexico on 16 July 2023.

Trees are symbolic for both clubs and feature on both of their badges.