London - Antonio Conte's Chelsea turned the Premier League title race into a procession in his first season, but worrying cracks are appearing that threaten to fatally undermine the current campaign.
The Stamford Bridge club accrued 93 points - the second-highest tally in the Premier League era - to finish seven points clear of nearest challengers Tottenham Hotspur and a whopping 15 ahead of Manchester City in 2016-2017.
But this term they are nine points adrift of pacesetters Manchester City, with three defeats already - the same as they suffered in the whole of last season.
Now the 2012 European champions are licking their wounds after an embarrassing 3-0 Champions League pummelling by Roma.
So what's gone wrong?
1. Lack of signings
Spain striker Alvaro Morata was Chelsea's marquee signing in the summer transfer window, joining alongside midfielders Tiemoue Bakayoko and Danny Drinkwater and defenders Antonio Rudiger and Davide Zappacosta.
But moves for several targets failed to come off.
England midfielder Alex Oxlade-Chamberlain opted for Liverpool and Spanish striker Fernando Llorente elected to move to London rivals Tottenham, while Ross Barkley stayed at Everton.
Perhaps most gallingly of all, striker Romelu Lukaku chose Manchester United over a return to his former club.
Conte expressed his frustration at Chelsea's failure to land some of his top transfer targets, but made clear he had no intention of walking out.
"I'm a coach, not a manager - the best of my work is on the pitch," he said.
"Then, for sure, when you want to strengthen your squad, you have to give your opinion to the club.
"They go to the market to try to help us. Sometimes it's possible, sometimes it's not."
2. Matic mistake?
Chelsea have been widely criticised for allowing defensive midfielder Nemanja Matic to join former boss Jose Mourinho at Manchester United.
Despite a strong-looking midfield roster that includes Bakayoko, Cesc Fabregas and N'Golo Kante, Matic's loss has been felt, particularly given that Kante has missed a chunk of fixtures with a hamstring injury.
Former England and Manchester United defender Phil Neville, speaking after the Roma defeat, said whoever decided to sell Matic should be sacked.
"What's gone wrong for Chelsea? One word: Matic," Neville told BBC radio.
"It's as simple as that. The minute they sold Nemanja Matic was a mistake.
"When you had Matic sat in front of you, alongside (N'Golo) Kante, there was protection. Whoever made that decision needs sacking. That is one of the poorest decisions I have ever seen in the Premier League."
Conte has also been hampered by injuries to key players.
Last season's player of the year Eden Hazard missed the first few weeks of the season, while Kante has not featured for the club in October. Right wing-back Victor Moses, who impressed last season, has also missed matches.
3. European distractions
Last season Chelsea had no European commitments after finishing a lowly 10th in the table in 2015/16, meaning they could focus all their attention on the Premier League, with ample time to rest between matches.
Despite their damaging 3-0 defeat away to Roma on Tuesday, they still look poised to qualify from Group C, but their continental exertions are putting a strain on Conte's thin squad.
"Roma proved to have more hunger, more desire, more will to fight and to beat us. We lacked everything," Conte complained after a Chelsea display scarred by some calamitous defending.
"We must find the hunger we showed all of last season and sometimes this season. But this season has been up and down. We need to find consistency."
Reports have emerged of players becoming unhappy with a tough training regime and Conte has admitted his squad is struggling to cope with the demands of defending the Premier League title and competing in Europe.
But in an angry outburst last week, he described reports of unrest at the club as "bullshit".
The Italian denied his reign has been undermined by players texting his former assistant Steve Holland to complain of his training methods and rejected a story that he will not see out the remaining 20 months of his contract.
"Around us there (is) a lot of bullshit. This is true. If I look at the past, I see it happened the same with the other (Chelsea) managers. A lot of bullshit," said Conte.
"They try to create problems between me, the club and the players. If someone is happy to continue to write this, I answer very well in the past. I am answering very well about these different issues."