Chelsea goalkeeper Thibaut Courtois credits their 100 per cent start to the season to manager Antonio Conte's tough regime.
Chelsea have won their first two league games 2-1 through late goals from Diego Costa, who scored in the 89th and 87th minute to beat West Ham and Watford respectively.
Courtois told the London Evening Standard: "We did a lot of physical work in pre-season and it means the players are ready to fight to the last minute for victories.
"In the Watford game and West Ham match as well, maybe we were able to run more at a high intensity until the end of the game.
"It's important to be able to do that in the Premier League. It is an extra quality to have. You see at the end of matches that teams have gaps because they can't cope with all the running. But we can cope - that is good.
"To win games late like we have done twice now is an asset to have. Obviously we hope to win games more easily, but when you win matches like this it tastes very good.
"It also usually means you are at the top of the table. I'm not saying we are going to be champions yet, but these victories mean that you can be there fighting for the title.
"If you want to win the League, it starts with winning difficult games like we did at Watford. We showed some great character."