That's the verdict of Antonio Conte in the wake of the Blues' 1-0 defeat to Manchester City at Stamford Bridge.
Chelsea marched to a second title in three years last season, ending the campaign seven points clear of second-place Tottenham.
But they've not had it all their own way since then and Saturday's loss was their was their second this term.
Chelsea are still one of the three early favourites to win the Premier League this time around - joined by City and Manchester United.
Conte knows he's got a battle on his hands to secure a fifth top division title of his managerial career though.
Conte said: "I see the commitment every day, but for sure to defend the title is very difficult. It is very difficult for every team in this league. To defend – it is very difficult to win two titles in a row.
"We won the title with Juventus and I was expecting a really strong challenge from AC Milan, but instead they sold Zlatan Ibrahimovic and Thiago Silva to PSG, so they became weaker. It wasn’t simple second time, but it was easier. Here, from last season to this season, you have big teams and now they are bigger.
"I think last season we did a really great job, because we won the league against a really strong team, because Man City last season also was a fantastic team.
"And now after I think a great transfer market, they have improved a lot. It’s not simple to play this league.
"We have to try to do our best in every game with great ambition, because we must always have the right ambition.
"But at the same time sometimes you have to compliment your opponent. You must be honest and accept the result."
Chelsea will be looking to get back to winning ways when they visit Premier League strugglers Crystal Palace on Saturday October 14.
