Krishanu began his professional career in the
Calcutta Football League with Police A.C. in 1979, and groomed under Achyut Banerjee. He later shifted to Calcutta Port Trust in 1980. After spending a couple of seasons there, he joined
Mohun Bagan in 1982. He played for Mohun Bagan until 1984. In 1982, he scored a debut goal against
Dempo Sports Club in the Strafford Cup. After a series of attempts from Ex-East Bengal recruiter Dipak (Poltu) Das, he joined their arch-rival
East Bengal Club in 1985 along with Bikash Panji and became an East Bengal legend. It was during his time in East Bengal, that made him known as the "Indian Maradona". He was part of the team that won
Federation Cup in 1985 and appeared in qualifiers of
1985–86 Asian Club Championship in Saudi Arabia. During his days in mid-1980s, the club was managed by legendary footballer and Olympian
P. K. Banerjee. In the Central Asia Zone (tournament named "Coca-Cola Cup"), they beat multiple foreign teams like
New Road Team of Nepal,
Abahani Krira Chakra of Bangladesh,
Club Valencia of the Maldives, and won the Coca Cola Trophy. He played for East Bengal continuously for a period of 7 years where he won many accolades including a treble (Durand Cup, Rovers Cup, IFA Shield) in 1990. He played for the club under coaching of
Syed Nayeemuddin. He returned to Mohun Bagan in 1992, and played alongside Nigerian striker
Chima Okorie, one of the best foreigners of the club. Krishanu again returned to East Bengal in 1994 for a season. He later joined his employer side – Food Corporation of India FC in 1995, which was also CFL outfit, having players like Narinder Thapa, Aloke Mukherjee. He played for them until his retirement in 1997. He was one of the highest paid Indian footballers of the eighties and along with his close friend and fellow midfielder
Bikash Panji with whom he formed a lethal combination on the field. His club transfer stories throughout the eighties and early nineties are very intriguing where the club dropped down to the level of crime to acquire his signature. ==International career==