Disaster struck Chelsea at Stamford Bridge on Saturday as Kalidou Koulibaly’s calamitous mistake gifted Leeds United a vital 3-0 victory.Disaster struck Chelsea at Stamford Bridge on Saturday as Kalidou Koulibaly’s calamitous mistake gifted Leeds United a vital 3-0 victory. The Senegalese defender, who arrived from Napoli with a hefty £34 million price tag this summer, was handed his first Premier League start. However, his inauspicious debut was shattered by an act of self-sabotage in the 84th minute. With the score locked at 2-0, Leeds launched a hopeful attack down the left flank. Patrick Bamford’s innocuous cross deflected off Marc Cucurella and fell into Koulibaly’s path. Inexplicably, the 31-year-old chose to control the ball with his chest before attempting to clear it away, only to see it bounce off his knee and into the back of the net. The goal sent shockwaves through the crowd and left Chelsea manager Thomas Tuchel visibly furious on the touchline. Koulibaly’s error gifted Leeds a two-goal cushion, effectively ending any hopes of a Blues comeback. To add insult to injury, Koulibaly was then shown a straight red card for a second bookable offense, compounding Chelsea’s woes. The dismissal leaves Tuchel with a significant defensive headache ahead of a crucial Champions League clash against Dinamo Zagreb on Tuesday. The defender’s blunder has raised serious questions about his suitability for the Premier League. Koulibaly’s reputation as a reliable center-back crumbled in an instant, leaving Chelsea with a massive hole to fill in their backline. Chelsea’s fans were left bewildered and frustrated by the player’s inexplicable mistake. The Blues have now conceded seven goals in their last two Premier League matches, a statistic that will undoubtedly concern Tuchel. The Koulibaly blunder will go down as one of the most embarrassing moments in Chelsea’s recent history. It remains to be seen if the Senegalese can recover from such a damaging error and prove his worth to the club in the seasons to come.