Cesar Azpilicueta, David Luiz and Gary Cahill started for the Blues, helping the side to keep their fifth consecutive clean sheet since Cote started fielding a 3-4-3 system.
Koeman, who played in a back three with Barcelona’s legendary ‘Dream Team’ of the 90s, says the formation is difficult to play against and if Chelsea keep their “winning mentality”, they will be fighting for the Premier League title.
“This system is very difficult to play against and the manager has brought a winning mentality to the players,” Koeman said, as reported by The Sun.
“If they can keep that then they will be fighting for the title.
“I have never seen a team so strong with this system.”
Eden Hazard, Marcos Alonso, Diego Costa and Pedro put five goals past the visitors in an intense performance that Koeman believes everyone can learn from,
Koeman added: “We can learn from that.
“It’s a big lesson for everyone.”
The Blues made 25 defensive actions during the game, also winning 64% of take-ons and 52% of tackles.
Chelsea are currently top of the table, one point ahead of Manchester City and Arsenal, while Everton sit sixth following the heavy defeat.