Football in India
National Football League, established in 1996 by governing body All India Football Federation (AIFF) was the first "semi-professional" football league in India. 
The League was renamed and restructured and the I-League was founded in 2006 after India's former top league the National Football League disbanded in a successful effort aimed at increasing the game in India. Links with clubs that were not in the I-League were maintained, and each season the bottom two clubs are relegated from the I-League and replaced by two from the I-League 2nd Division. The I-League is currently contested between 11 clubs. The Kolkata Derby in the I League (and other tournaments) played between Mohun Bagan and East Bengal is one of the most fierce rivalries in the world (featured in FIFA website) and one of the oldest derbies in the world (90 years). An average 80, 000 to 100, 000 supporters throng the stadium in this special fixture.
Indian Super League
During the first three seasons of the Indian Super League, attendances across the league had exceeded expectations of pundits and of the domestic I-League. Television ratings were also strong for the league as well as social media interaction. However, despite the general success off the pitch, the league drew criticism in other areas. Due to the need to accommodate the ISL into the Indian football calendar, the I-League season was shortened and went from having an October to May schedule to January to May schedule. Indian players would play for both an ISL team and an I-League club while the I-League continued to suffer from lack of visibility compared to the ISL. India head coach Stephen Constantine had called for both the ISL and I-League to either run together at the same time or merge.