Lampard won a Champions League, three Premier League titles and four FA Cups, amongst other honours, with the Blues before leaving in 2014.
And he revealed that striker became a ‘different Didier’ before big games.
“John, I wouldn’t say he’s underrated because everyone appreciates how good he was but I think he’s underrated on the ball, how good he was.
“Didier for me was amazing, to have him in your team in a final, you felt Didier in the dressing room before a big game that it was a different Didier, he was like an animal.
“His preparation, the intensity in his eyes and then he always produced.”