John Boyd, who was hired as Bishop Noll's boys basketball coach in August, resigned on Friday.
Boyd's departure was confirmed by a source close to the program.
Assistant Murray Richards, a former head coach at West Side, served as acting coach on Friday when the Warriors beat Griffith 61-57 to improve to 3-3 overall and 1-1 in the Greater South Shore Conference.
Boyd was hired on Aug. 30 to replace Josh Belluomini, who resigned after six seasons.
It was the third Region stop for Boyd, who spent 10 seasons each at West Side and Michigan City before coming to Noll.
Boyd's West Side teams went 143-65, winning the Class 4A state title in 2002 and a regional in 2005. At Michigan City, his teams were 128-113.
The Wolves were 10-14 last season and have not won a sectional since the school was formed by the consolidation of Rogers and Elston in 1995.
Richards was head coach at West Side from 2012-15, guiding the Cougars to a 32-26 record.
Noll's next game is Saturday at home against Lake Station.