Chelsea will have to overturn a 1-0 deficit at Stamford Bridge after they were stunned by Championship side Middlesbrough in the first leg of their Carabao Cup semi-final. Mauricio Pochettino's men lost a League Cup match to lower-league opposition for the first time since 1999 but the former Tottenham head coach believes his side played well. He said: "The pressure was good and intensity, we cannot say anything.  "We made some mistakes in the first half, we gave them chances to scores and they were so aggressive and tough. They play in the transition with the counter-attack and in a block really deep and it was difficult for us to break down.  "We had too many chances to score when we didn't score, that is football. We are disappointed but it is the first half of the tie. We need to be positive." Chelsea missed several big chances and enjoyed 72% possession at the Riverside Stadium but it was not enough to down Michael Carrick's resilient squad. Poch, 51, added: "If you assess the performance, overall we were the better side, we created more chances and had the clear chances.  "But we didn't score. That has happened this season and there has been a lot of games we have not won because we were not clinical enough. "We have a lack of goals but not creating chances. We are creating many chances but not scoring them and if you don't score it is difficult to win." The Blues will have the chance to make up for their mistakes in the capital on January 23, with a place in the final at Wembley on the cards and within touching distance for both sides.