Head coach Mauricio Pochettino has admitted that Chelsea have failed to make their dominance count on too many occasions this season.
Chelsea went into the first leg of their EFL Cup semi-final with Middlesbrough on the back of scoring seven goals in games against Luton Town and Preston North End.
However, the Blues squandered a wide array of chances in the first half at the Riverside Stadium, with Cole Palmer the guilty party on several occasions either side of a winning goal from Hayden Hackney.
While Chelsea dominated the second half as they searched for an equaliser, clear-cut opportunities were few and far between as Boro held on for a famous victory.
The Premier League outfit must now await two weeks for their chance to overturn the 1-0 deficit at Stamford Bridge, with their initial priority being a top-flight game against Fulham on Saturday.
Speaking to Sky Sports after the game, Pochettino was rueful over the openings that went begging, yet opted to remain positive after his side controlled possession of the ball for large periods.
Pochettino said: "Today 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 then 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."
He added: "We have to be pushing. If you assess the performance, then 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 then it is difficult to win."
After Saturday's West London derby, Chelsea will have a 10-day break before they face Boro in the reverse fixture on January 23.
