The left-back has struggled for regular football at Leeds United.
Both were exciting and expensive signings but only one has really had an impact at Stamford Bridge.
Whilst Costa has been banging in the goals, scoring 20 goals this season, Luis has spent much of it on the sidelines. The Brazilian has failed to overcome Cesar Azpilicueta in the left-back position. He has started just 12 Premier League games this season.
His lack of action recently saw him linked with a move back to the Vicente Calderon by the Daily Mail.
But speaking to Marca, Costa has hinted that he will not be heading back to the Spanish capital:
"Filipe is there, is not passing his prime as a player.
"He is one of the best left-backs in the world. With the quality he has and capacity is very important despite not playing many minutes.
"We all know what he can bring.The coach does not think he will let him go.He will bring a lot."
As much as Luis has failed to shine he is a player Chelsea need. They need proper coverage across the pitch and that means Luis is necessary to keep Azpilicueta on his toes.
Hopefully next season he can get some more regular first team action.