Luiz Felipe Scolari has warned the rest of the Premier League that Chelsea will be even better in the second half of the season.
Chelsea are currently top of the division on goal difference from Liverpool but face Arsenal in a London derby at Stamford Bridge on Sunday.
Victory for the Blues would put them 13 points clear of their rivals and effectively end their title ambitions for another season.
Chelsea, unbeaten away from home, have dropped nine points at Stamford Bridge but Scolari expects the Blues to be even better once he gets all his injured players fit again.
Scolari is without Juliano Belletti, Franco Di Santo, Michael Essien and Ricardo Carvalho against Arsenal, and striker Didier Drogba is suspended.
"It is a must-win game for us," said Scolari. "What I said to my players one month ago is that we need to arrive between November 15 and until the last day in December in a very good situation, with all players in good fitness.
"When I have squad players in good condition, then I'll have the players to challenge in all competitions. We'll be better in the second half of the season."
Chelsea have failed to beat Manchester United and Liverpool at home so far this season and despite all the off-field problems suffered by Arsene Wenger, Scolari expects a difficult contest against his old friend.
He said: "Arsene has been there 12 years and he's a man who builds teams. Arsenal are very good every year and when you change two or three players in one season, you need time. The time, I think, for Arsenal and Arsene is now.
"Arsene and I have the same ideas about football. Our personalities are different but we have the same ideas about the game.
"I like his style. He's a very good friend whether they win, lose or draw. I like him and I think he's my friend. I like him as a coach.
"We are opponents only for 90 minutes. After the game, I'll invite him to come and talk - win, draw or lose. We are two friends. But, in the game, we are opponents."
Over the last few years, Chelsea have spent big money on star names while Arsenal have developed an exciting crop of young talent.
Scolari now firmly believes that in the current financial crisis, there is much for Chelsea to learn from Arsenal's philosophy.
"Chelsea are trying to learn," he added. "We are trying to work with young players in the academy.
"Chelsea were a club that spent money four or five years ago, but not now. With me, we've only spent on Deco.
"Arsenal haven't spent money only on players. Coaches and boards need to think about money. It's not easy any more.
Maybe two or three years ago, there was more money. Now there's less. We need to think."