Manchester City earned a 1-0 win over Chelsea at Stamford Bridge on Saturday courtesy of a goal from Gabriel Jesus.
The visitors dominated proceedings from the blast of the whistle but the first half ended 0-0.
Gabriel Jesus scored a scrambled effort just after the restart to give City a vital win.
“We were excellent, but only in the last 20 metres of the pitch not the other 80 metres,” said Tuchel. “Part of the performance is to make your opponent underperform and City did that.
“We lacked belief and confidence to escape (the pressure). With every mistake we did, we lost more confidence. In the end we defended the box and the goal very well but it was too deep.”
Chelsea will hope to bounce back in their next match against Juventus in the Uefa Champions League.
