Manchester City are 11 points clear at the top of the table after winning an unprecedented 15 matches in a row, while Antonio Conte's Chelsea trail them by 14 points in third place.
"We must try to find the right solution to contend the title, to try to fight them. Not only Chelsea, but the five top teams.
"Manchester City are not a surprise for me. At the start of the season all the people said the league was for two contenders - Man City and Manchester United.
"This is a great team, but this team was a great team last season.
"During the transfer market they reached their targets. We must pay great attention, not only in England, because Man City is building a strong team to lead in Europe.
"I think also you must be lucky, because in many games they won in the last minute.
He added: "Time is moving on and Manchester City are continuing to win, this is the problem.
"We must be realistic. In the last nine games we won seven times, drew one - to Liverpool - and lost one. And the distance improved for Manchester City.
"In nine games, when you win seven times and draw only once - it's possible to draw against Liverpool - and lose only one game, and stay 14 points less…"