Chelsea had 9 players at the 2006 FIFA World Cup: Petr Čech, John Terry, Frank Lampard, Joe Cole, Ashley Cole, Michael Essien, Ricardo Carvalho, Arjen Robben, and Didier Drogba.

Chelsea players by country

Player| Country
---|---
Petr Čech| Czech Republic
John Terry| England
Frank Lampard| England
Joe Cole| England
Ashley Cole| England
Michael Essien| Ghana
Ricardo Carvalho| Portugal
Arjen Robben| Netherlands
Didier Drogba| Ivory Coast

The exact count can vary depending on whether you mean players contracted to Chelsea at the time or players later associated with Chelsea, but for the 2006 tournament squad lists, the number above is the standard answer.