Chelsea boss Thomas Tuchel delivered an honest verdict following his side's 1-0 victory over Zenit in the Champions League group stage.
Romelu Lukaku's second half header saw the Blues come out on top.
Speaking to BT Sport after the game, Tuchel discussed the match.
He said: "We had to find little spaces and moments to shoot and create chances. It was a deserved win but hard work. They are the Russian Champions, it was a hard match. They made us tired with their high intensity."
The Blues struggled in the first half and went into the break tied, without registering a single shot on target.
"We expected a tough one because it’s the highest competition in Europe," Tuchel continued.
"They have a lot of quality players. We had to be on our top level, like I said, I’m happy because we had to work a lot. It’s not easy, it is good to constantly perform on that level. Winning and another clean sheet is super important for the belief and for our process. We are not finished but we are in a good place to improve."
Next up for Chelsea in the Champions League is an away trip to Juventus, who began their campaign with a 3-0 win away to Malmo.
The Italian giants are Chelsea's toughest opponents in the group and Tuchel will be keen to get a positive result as Tuesday's goalscorer Lukaku returns to Italy, where he played for Inter Milan last season.