Chelsea boss Antonio Conte fears Manchester City's "incredible" improvement this season could turn the Premier League race into a procession as the defending champions struggle to stay in touch.
Conte's men rescued a late point at Liverpool on Saturday, with Willian's unexpected cross-shot finding the top corner to cancel out Mohamed Salah's opener but they are now 11 points adrift of top spot.
Chelsea's Italian boss believes Pep Guardiola's work in the summer transfer market was crucial in taking City to the next level and is mindful another round of spending could be coming when the window reopens.
"Manchester City's path is incredible, no?" said the Italian.
"I think Manchester City in this season is a strong team. Also last season, Manchester City was a fantastic team. Then, after the transfer market, they bought their first targets and then they have improved a lot.
"They can do this also in January maybe, in the future. For this reason we must be worried because if we want to compete with Manchester City we have to work and then make the best decisions in the transfer market."
Chelsea goalkeeper Thibaut Courtois said the hectic winter fixture list could prove tricky for City and let the chasing pack back into the title race.
"We have to be there to keep on winning and hopefully close down on them, then towards the end of the season maybe overtake them. But at the moment they are the best team in the league and it's hard for them to drop points."
Conte's spirits have been lifted by the return to fitness of wing-back Victor Moses, meaning the only absences from his first-team squad are Michy Batshuayi, Charly Musonda and Kenedy -- none of whom are regulars.
"Now, first of all I have all my players," he said.
"To have all my players will be very important because we have to face a game every three days and it will be very important.
"I only ask for one thing: to have all my players available, because in our squad there are 16 senior players and I trust them."