Chelsea have won 10 straight Premier League games, they are six points clear at the top of the table and their progress towards the title seems inexorable. But are Antonio Conte's team really that good? Can they answer some critical questions?
Q Long term, is three at the back really that great an idea?
A Few managers are as steeped in the system as the former Italy coach.
"They're a really technically good, well-balanced, team but I don't think that, in the history of the Premier League, a team have won the game playing three at the back throughout a whole season," Sunderland manager David Moyes says.
"The difference with Antonio Conte is that he's played in and coached that system and knows it inside out but Chelsea can also play four at the back effectively."
Q How important is Conte's appreciation of the art of catenaccio?
A Their resilience has enabled Chelsea to keep eight clean sheets during 10 straight top-tier wins, conceding only two goals along the way.
"It's amazing," says wing-back Marcos Alonso.
"But it's not just about the system. It's that our team's working very hard. Everyone puts everything into defending and we have also to thank Thibaut Courtois in goal."
Q Are Chelsea stronger than their rivals in mind and body?
A It looks that way.
"We're getting used to winning," Alonso says. "And we want to keep the amazing atmosphere in our dressing room that comes with winning but we know we've got to be at 100 per cent every game because it's a tough league.
"The manager hasn't changed with success, he hasn't mellowed, definitely not. He wants the players to keep giving everything and we know that's very important."
Then there is the fitness aspect.
"From the start of the season we've worked a lot on physical aspects and we continue to work on them," Conte says.
"In this league it's important to have intensity and strength as well as good technique. This league's very tough so, if you're not strong, it's difficult to win."
Q What happens if Diego Costa, Victor Moses or Alonso are injured?
A With his aggression now controlled, Costa increasingly looks the complete centre-forward and his loss would be a big blow.
Nonetheless Chelsea do have a £29 million (S$52.1 million) striker on the bench in Michy Batshuayi. Moreover, a revolving front three of Willian, Eden Hazard and Pedro would not necessarily be too shabby.
In one sense losing the width and zip provided by Moses and Alonso could arguably prove more damaging to an otherwise rather narrow team.