Cape Town - Chelsea
midfielder Nemanja Matic has given Premier League title rivals
Tottenham credit for keeping the Blues on their toes this season.
Antonio Conte's charges seemed to be running away with the league after beating Stoke City on March 18, but defeats against Crystal Palace and Manchester United gave Spurs an opening.
Chelsea beat Everton 3-0 away from home at the weekend to maintain their lead at the top of the standings, but Spurs also won to stay within four points.
"I think this year is more difficult," Matic told the press, according to ESPN FC. "We finished 2015 eight points clear of Man City. I'm not sure this will be the case with Tottenham.
"I'm sure they will not give up until end of the season. At this moment it's hard, but we will see. Each time we win, they win, two years ago that was not the case."
He added: "This season is hard. We win and Tottenham win, they are always close. But the important thing is that we are playing well, we take points and we will see if they can drop some points.
"They have some difficult games, home and away, so everything is open until the end."
Meanwhile Cesc Fabregas didn't start against Everton on Saturday, but manager Antonio Conte praised his contribution off the bench.