Kawhi Leonard has statistically been one of the worst on-ball defenders in the NBA this season. According to nba.com tracking data, opponents are shooting 55.9% when guarded by him, compared to an expected FG% of 46.6%. That 9.3% gap is the 5th worst in the entire NBA.
Source (not counting players with too few attempts to qualify)
Expected FG% is based of the shot tracking data
Sometimes this data isn’t entirely accurate but it would definitely explain part of why the Clippers have been horrible on defense even when he’s playing and generally speaking this stat has a pretty strong correlation with defensive rep LaMelo is as bad as this and Luka/Jokic also aren’t good while guys like Giannis Wemby and Gobert are elite
EPM also has him as a negative defender not this bad but 29th percentile