Thomas Tuchel acknowledged Edouard Mendys huge error cost Chelsea dearly after the 10-man Blues slipped to a demoralising 3-0 lo s at Leeds United.Mendy inexplicably allowed Brenden Aaronson to steal po se sion on the edge of the six-yard box andpoke Leeds into a 33rd-minute lead.Further goals from Rodrigo and Jack Harrison helped the hosts claim their first win over Chelsea since December 2002.Kalidou Koulibaly was then sent off after picking up a second booking as Chelseas miserable outing drew to a close. It was the defenders sixth league Yasmani Grandal Jersey dismi sal since the start of the 2017-18 season more than any other player in the top five European leagues.But it was Mendys dismal mistake which put Chelsea on the back foot, and Tuchel did not hide his frustration with the Senegal goalkeeper after the match.Asked whether he would discu s the incident with Mendy, Tuchel said: He knows himself. With these kinds of mistakes, I dont think we need to speak a lot.He knows himself that this was a mistake and honestly, this has nothing to do with protection or no protection.Everybody in the world sees the mistake, its a huge mistake in a crucial time of the match. It does not help and hes Clayton Kershaw Jersey the one that is the most disappointed because it cost us a lot today. Speaking to Sky Sports, former Manchester City and Newcastle United goalkeeper Shay Given was equally critical of Mendys decision-making, saying: He just has a really poor first touch and his heads a bit scrambled at that point. Worst case, kick it out for a corner, just dont do what you do.The only thing I would say in Edouard Mendys defence, not too many Chelsea defenders have run into a position to receive the ball from him.But its still a terrible mistake from Mendy, he Cody Bellinger Jersey knows he has to clear his lines. Its a poor, poor goal to give away.The defeat at Elland Road represents another blow for Chelsea, who conceded a last-gasp equaliser against London rivals Tottenham in their previous match. Leicester City Justin Turner Jersey defender Wesley Fofana has been strongly linked with the Blues as Tuchel bids to strengthen his defence, but the Chelsea bo s insists his existing squad should be performing better.We need to wait. The transfer period is still open. It gets later and later and we need to focus on what we have and what we can do, Tuchel said.We can obviously play at a high level, but we lost track when there was no need. We were not forced to lose track. Everything was going well.We can win with this team in Leeds, everything was going well and we had goalscoring opportunities. It went the other way and I think it was more our fault than anyone elses credit.While a defensive addition remains an aim, Tuchel was dismi sive when Fernando Valenzuela Jersey asked whether Chelsea could target a new midfielder, responding: Another midfielder? We have Jorginho, NGolo Kante, we have Ruben Loftus-Cheek, Conor Gallagher, Mateo Kovacic.They Kovacic and Kane are injured, yes, its a problem. But they will come back. Theyve not disappeared.Chelsea host Leicester City in their next Premier League game on Saturday, having claimed four points from their three outings this season.