Saturday morning's practice was held in damp to wet conditions, a portent of things to come.
Qualifying later in the day became a lottery, continually interrupted by red flags as drivers slid off the circuit in the now very wet conditions. With cars stopped in dangerous positions, qualifying was stopped three times.
Cassidy never got a chance to string enough laps together to warm up his tyres properly in the cool conditions and set a competitive time. He was only 16th fastest.
The conditions had worsened by Sunday and all racing was cancelled before any car had even ventured onto the track in the morning warm-up.
Cassidy can still finish his Japanese season on a high in three weeks' time, when the final round of the Super GT series - Japan's equivalent to V8 Supercars - is held at Motegi.
With co-driver Ryo Hirakawa they go into the meeting with a six points lead in the championship in their Lexus LC 500.