The Black Stars centre-back was handed his marching orders after 22 minutes following a reckless tackle on Alaves’ forward Toni Matrtinez.
Referee Adrián Cordero Vega had initially shown the Ghanaian a yellow card before a Video Assistant Referee review led to a straight red card.
Despite being ten men down for most of the game, Vallecano scored late through an own goal from Antonio Sivera to secure all three points.
Meanwhile, Abdul Mumin started the game as Rayo Vallecano’s Player of the Month for September following an outstanding start to the season.
The Right to Dream Academy graduate will miss the matches against Villareal, Las Palmas and Sevilla.
Abdul Mumin has made 11 appearances, scoring a goal and delivering an assist in the La Liga for Rayo Vallecano this season.