Madrid giants Real Madrid and Atletico Madrid will renew their historic rivalry on Sunday in a blockbuster derby in La Liga.Los Blancos are currently running away with the league, sitting eight points clear at the top of the league standings and ten ahead of the Rojiblancos. Carlo Ancelotti's swashbuckling side are on a nine-game winning run across competitions. They haven't lost in 12 games since a 2-1 reverse at Espanyol in October.Meanwhile, Atletico, the reigning champions, have stuttered lately, with erratic results wreaking havoc on their title defence. Another setback on Sunday will be a real blow. However, they haven't won in the Madrid derby in seven attempts since 2016.Nevertheless, we have a crunch game on our hands to spice up the weekend. On that note, here are five key players who could shape the outcome of the 228th El Derbi Madrileno:#5 Casemiro (Real Madrid)The glue that binds Madrid togetherAs far as holding midfielders go, very few can hold a candle to Casemiro. He been at the heart of Real Madrid's immense success in the last few years. He offers balance to the side, and is a strong connection between defence and attack, while playing a crucial role in transitions.The Sun Football ⚽@TheSunFootballChelsea are reportedly interested in signing Real Madrid midfielder Casemiro2:22 AM · Dec 11, 202115Chelsea are reportedly interested in signing Real Madrid midfielder Casemiro https://t.co/To2xwSP5kyA crunch tackler with impeccable vision and a penchant for amazing long-range strikes, the Brazilian has three assists for the season. He could be vital in breaking down Atletico's attacking play, with his ball-winning ability and close man-marking.#4 Thomas Lemar (Atletico Madrid)Lemar is rapidly developing into a world-class prospect.His start to life in Madrid after arriving from Monaco wasn't plain-sailing, but Thomas Lemar has truly come of age this season. In fact, many Atletico faithful rate him as their best player right now, with the Frenchman consistently delivering top-notch performances.Atlético de Madrid@atletienglishWhatever the question, Thomas Lemar is the answer.8:01 AM · Dec 3, 20213216Whatever the question, Thomas Lemar is the answer. https://t.co/aNTIzJFHkiA prolific dribbler with strong passing ability and set-piece prowess, Lemar has scored thrice and made two assists in seven starts this season.