Arsene Wenger believes N'Golo Kante - a player he repeatedly tried to sign for Arsenal - is the key figure in Chelsea's Premier League title charge.
Wenger's men travel to Stamford Bridge on Saturday sitting third in the table, behind Tottenham on goal difference and 10 points shy of Antonio Conte's leaders following a dispiriting 2-1 reverse against Watford on Tuesday.
Chelsea drew 1-1 at Liverpool on the same evening and Wenger recognised a familiar stand-out performer in ex-Leicester City midfielder Kante, who is on course for a second top-flight title in as many seasons.
"I watched their game against Liverpool and N'Golo Kante had a huge impact," said Wenger.
"It's not a coincidence that they are in the position they are and Leicester were in the position they were in last year
"[Diego] Costa and [Eden] Hazard have come back to very good form so they are very efficient when they go forward.
"And, as I just said, N'Golo Kante has had a huge impact."
Another injury setback for Aaron Ramsey, Santi Cazorla's long-term absence, Granit Xhaka's ongoing suspension and Mohamed Elneny being on duty at the Africa Cup of Nations leaves Wenger short in central areas.
It is a part of his squad he admitted he wanted to bolster with Kante, both when the 25-year-old left Caen for Leicester and last close-season.
"Yes," said Wenger when asked whether he tried to but the France international. "When he was in France, when he was at Leicester."
He was less forthcoming on why a deal could not be done.
"Again, I cannot explain to you absolutely everything, but it is quite obvious where he has gone," added the Frenchman.
"Transfers are transfers, you cannot explain absolutely everything."
A player under consideration for Wenger is Monaco teenager Kylian Mbappe, whose displays for the Ligue 1 leaders this term have drawn comparisons with Thierry Henry.
Wenger tried to bring the 18-year-old forward to Emirates Stadium last season and acknowledges the parallels with a great revered in both north London and the principality where he made his professional breakthrough.
"Yes, there are similarities to Thierry Henry," he added. "He is from the Caribbean as well. He is a huge talent, he plays for Monaco and Thierry Henry played for Monaco
"You can see the similarities, but what makes the career after that is the mental aspect that Theirry had. This young boy has to show that he has the same qualities.
"It [a transfer bid] was at stake last season, but he decided to stay where he was."