LONDON -- Jose Mourinho said it will be impossible for his table-topping Chelsea team to go through the entire Premier League season unbeaten.
Chelsea's title challenge floundered last season when they lost against Crystal Palace at Selhurst Park in March, yet Eagles boss Neil Warnock said ahead of Saturday's game between the two sides that the enhanced Blues squad could be unbeatable this season.
A decade has passed since Arsenal famously achieved the feat of going through an entire Premier League campaign without losing a match, yet Mourinho believes it is highly unlikely their achievement will be equalled.
When asked whether his team could complete the 38-game campaign without defeat, Mourinho replied: "I don't think so. Times change, teams change, competitions change, players' mentalities change. Everything changed, so I don't think it's possible in England any more.
"We are a good team, we know that we are a good team. We know that we have a long way to go, a lot of space to improve. We have a lot of young players and we are in the most difficult competition in the world, which is the Premier League. It is the only competition where every result can happen at every stadium and especially because we have five teams fighting for the title.
"We know the team we are building and obviously the feelings we have are very good, but I am not in hell when things are not going well. I'm not in paradise because we are doing well."
Despite opening up a nine-point gap on Arsenal with a victory against the Gunners right before the international break, Mourinho insisted the Premier League title race was still a five-team battle that also includes Louis van Gaal's Manchester United.
"I think the same five that were at the beginning of the season, they declare their ambitions," he stated. "There are lots of good teams in this league, but they come after the five contenders.
"With all the respect, I don't think they will break the control of the top ones, but I think all of us, the two Manchester teams, us and Arsenal and Liverpool, all five we are title contenders. That is my opinion."
Mourinho then addressed the ongoing issue surrounding the fitness of his free-scoring striker Diego Costa, after the Spain striker played in both of his country's Euro 2016 qualifiers despite claims from the Chelsea boss that he is carrying an ongoing injury.
"He is a big doubt," Mourinho said as he assessed Costa's chances of playing at Palace on Saturday.
"The Spanish team played in Luxembourg on Sunday. I gave them Diego, [Cesc] Fabregas and [Cesar] Azpilicueta, so I gave these players Monday and Tuesday off. They need to report to train on Wednesday 3pm. Diego was here Monday at 9am. So you can imagine how strong he was to be here Monday at 9am.
"I didn't speak to the Spanish federation. I don't speak with national team managers unless they want to speak with me. I am powerless and because I know that, I don't lose my time contacting the national teams.
"During my career, some of them used to contact me. They ask me about the situation about our players. When they decide to contact me, I am open to speak with them. It is never my initiative to contact national teams and national team coaches. They have the power, we don't have the power."