Antonio Conte fears Chelsea face a tough task to hold on to top spot in the Premier League table as he feels the English top flight is stronger than ever before.
The Stamford Bridge side beat Middlesbrough 1-0 on Sunday to leapfrog Liverpool and go top of the table, much to the delight of Conte.
However, the former Juventus boss has warned his team they are not there just yet due to the quality of their rivals.
"I am particularly happy for the players that we sit atop of the table at the moment. It is not only a reward for our hard work, but also shows that we are on the right path," Conte told La Gazzetta dello Sport.
"We should not forget that we were in a bad situation after we lost to Liverpool and Arsenal six weeks ago. It will not be easy to remain top of the table until the end of the season.
"This Premier League season is perhaps the most difficult one ever. We have to battle it out with Arsenal, Liverpool, Manchester City, Tottenham and Manchester United. You do not have such excellence in any other league in the world.
"I want to show Chelsea that they made the right choice to appoint me for the next three years. That counts even more than winning titles.
"It has definitely helped me that we are not in Europe and that I had the entire team available all week when I had just started. It allowed me to work on the foundation.
"I started out with a 4-2-4 formation, just like at Bari, Siena and early on with Juventus. I then switched to 3-5-2 and eventually to 3-4-3 because it suits the team best. But Chelsea are a club that should always be in Europe."