Pep Guardiola has never lost to Maurizio Sarri in three meetings and the Chelsea boss admits he is still unsure how to beat his Manchester City counterpart.
Chelsea welcome the Premier League leaders to Stamford Bridge on Saturday in a mouth-watering encounter, with City sitting 10 points clear of Sarri's Blues.
After going 12 games unbeaten at the start of the season – Sarri setting a new record for a debutant Premier League manager – Chelsea have stuttered of late, losing ground in what looked set to be a three-way title battle with City and Liverpool.
Victory on Saturday would launch Chelsea back into contention, but Sarri concedes picking apart a Guardiola side is still something he is working out how to do.
When asked at his news conference how his side could beat City, Sarri replied: "I don't know!
"Against Guardiola I have lost every match, so I don't know. You'll have to ask someone else!"
City come into the clash unbeaten in the Premier League this season, winning their last seven top-flight games, and Sarri believes Guardiola has the strongest team in Europe at his disposal.
"The match for us is really very important," he added. "We know it is a very difficult match against, maybe, the best team in Europe. So, we know it is very difficult.
"It has been impossible to beat them for a long period but in a match everything can happen.
"I think that we are improving, but they are improving also, so it is difficult to recover the gap.
"We started the season well now we have to face some difficulties, it's normal to have some difficulties with a new way of playing.
"We have to try and solve problem by problem, day by day, to improve in a definitive way."Published 07 Dec 2018, 18:52 IST