Antoine Griezmann scored the only goal of the game as Atletico Madrid sentenced Espanyol to their sixth consecutive defeat in LaLiga.
Oblak, Arias, Godín, Savic, Saúl, Correa (Montero, 71'), Rodrigo, Thomas (Gelson, 76'), Koke, Kalinic (Vitolo, 64') y Griezmann.
Diego López, Rosales, David López, Naldo (Melendo, 72'), Dídac Vilà (Pedrosa, 82'), Sergi Darder, Óscar Duarte, Granero, Baptistao, Borja Iglesias y Sergio García (Piatti, 69').
1-0, min. 55. Griezmann, de penalti.
Melero López (colegio andaluz). Mostró tarjetas amarillas a: Oblak (85') y Granero (88').
Partido de la jornada número 16 de LaLiga, disputado en el Wanda Metropolitano.
Griezmann struck from the penalty spot in the second half as Atletico temporarily moved level with league leaders Barcelona, who host Celta Vigo at Camp Nou later on Saturday.
Espanyol had their chances but were made to pay for not taking them when Esteban Granero gave away a spot kick.
Atletico are now unbeaten in their last 14 games in the Spanish top flight, their third longest unbeaten run in the league since Diego Simeone took charge in 2011.
The Rojiblancos will look to maintain their form in the New Year as they fight with Barça for top spot and look to recreate their 2014 title success.