In his new autobiography, entitled 'Commitment', Drogba spoke of the first training session he undertook with the Blues after joining from French club Marseille in July 2004.
The Stamford Bridge legend admits he knew little about the West London club prior to his move and has confessed that he thought captain Terry was actually a reserves player getting some experience with the senior squad.
"I noticed a tall, strong guy who looked so young, and who walked and carried himself in such a way that I assumed he was from the reserves," Drogba wrote in his new book as serialised by the Daily Mail.
"That's interesting,' I thought. 'They've obviously brought him over to get a bit of senior squad experience.'
"Towards the end of the session I asked another player who the young guy was. 'It's the captain!' he replied, laughing. 'John Terry.'
"That's how little I know about the team – I hadn't even recognised their new young captain."