Back-to-back Premier League defeats by Liverpool and Arsenal in September forced Chelsea manager Antonio Conte to adopt the tactics that have sent his team on an 11-match winning run in the top flight.
Chelsea beat Crystal Palace 1-0 on Saturday to stretch their lead at the top of the table to seven points and equalled a club record for consecutive Premier League wins.
Conte's men were beaten 2-1 at home by Liverpool in September before losing 3-0 at Arsenal, and the manager said the defeats by title rivals had prompted him to change his formation and sparked his players into life.
"Usually when I don't win it's very difficult to sleep, but now I'm sleeping the right (amount)," Conte told British media. "After 11 wins, we have a positive pressure that we want to continue.
"I like to win, and to see my teams have two bad defeats - we deserved two bad defeats -- I didn't like this and I tried to find the right solution on the pitch, outside of the pitch.
"We found the right solution with the players, to explain that we all deserve better than last season."
The Italian also said he was initially concerned about whether his players would be able to adapt to the new formation and if he was changing too much too soon.
"In the history of Chelsea, this never happened, no? To change it totally, this situation, is not easy -- you must go slowly, slowly, and to put the idea (across)," he added.
"You always hope not to make great changes to the team. I have players that had only played with four (in defence)."
The league leaders host Bournemouth on Dec. 26 and Stoke City on Dec. 31, before visiting Tottenham Hotspur on Jan. 4.
(Reporting by Hardik Vyas in Bengaluru)