The pair spent a two-year spell together at Atletico Madrid, both playing in the 4-1 victory over Chelsea in the UEFA Super Cup in 2012.
Since that game, during which Falcao scored a hat-trick, their careers have taken different paths, with the Colombian forward moving to Monaco and suffering a severe injury, before signing on loan with Manchester United this summer. Luis remained with Atletico following Falcao's departure, winning La Liga last season, and then signing for Chelsea alongside Diego Costa at the beginning of this campaign.
Their respective English careers have got off to average starts, with Luis struggling to break into the Blues first-team due to the form of Cesar Azpilicueta, whilst Falcao has looked out of sorts in his early displays, although he netted his first goal for the Red Devils in the 2-1 victory over Everton at the beginning of October.
However, the pair will likely face off on Sunday, with Chelsea travelling to Old Trafford in the key Premier League fixture. Azpilicueta is starting a three-game suspension following the red card given in the victory over Crystal Palace, whilst Falcao will be tasked to lead the line against the second best defence in the top flight.
Despite starting the season with an unbeaten run stretching to eight games in the league, Luis has warned his teammates to be wary of United’s new star, with the forward a better striker now than he was when he last faced the Blues.
Speaking to the Standard, Brazilian international Luis said: “Falcao is a better striker now than he was at Atletico for sure. He was injured and changed clubs so he wants more. He is not resting right now. He is a tiger and wants to score more.
“He is a brilliant striker. He fights for every ball and is probably the best in the world with his head.”
Despite lavishing heavy praise on the forward, Luis is confident that Jose Mourinho has prepared his team for any challenge they will face this season.
He added: “Will I give my team-mates any special advice on how to stop him? No. Our team is prepared for anything, not only Falcao.
“Manchester United have a lot of dangerous players. We have to be prepared."