Pat Riley — Sued Over Leaky Basement

He”s crushed the Celtics … the Bulls … and now NBA legend Pat Riley is accused of destroying his neighbor”s basement … this according to a new lawsuit obtained by our sources.

According to the docs, Riley and his wife Christine own a beachfront property in Malibu … which he overhauled in 2009 with new landscaping, remodeling, terracing and a new irrigation system.

Everything seemed hunky dory … until Pat”s next-door neighbors began to experience some major leakage at their property a short time after the Rileys completed their work.

In the docs, the neighbors allege their special “French drainage” system was collateral damage in the Riley renovation project … and as a result, their basement flooded. .

Now, the neighbors want the Rileys to pay up for all of the trouble they caused … and they want no less than $551,000.