Pennant: Ashley Cole is a little rat
The 28-year-old, who arrived from Arsenal in 2006, has made 91 league appearances for the Blues, but took time to find his best form for the Stamford Bridge side.
However, the England international netted in successive home league games for Carlo Ancelotti's side against Burnley and Tottenham Hotspur, before sustaining a knee injury in the Blues' shock defeat to Wigan Athletic.
And former Liverpool and Birmingham wide-man Pennant, who was a team-mate of Cole's at Arsenal during his six-year stay with the Gunners from 1999-2005, believes the left-back's tenaciousness makes him one of the toughest full-backs in world football.
"Ashley is probably the best left-back I have played against. He is so annoying, like a little rat," he told People.
"You think you have got past him and there he is in front of you again.
"As soon as me and him cross the white line we lose that friendship, but it would be great to be back in a squad with him."