I guess I'm the only person who ever heard of his solo hit "So Wrong". It was played on a station I happened to be listening to.
I never heard it. It peaked at #30 in the Billboard chart. Maybe regional. Certainly not the kind of song on can build a 35 year touring career on, compared to the solo hits by Michael McDonald. Which may be why he quickly rejoined the Doobie Brothers. He is the member who has been with the band the longest. The only time he was away from the band was the 5 years (1982-87) when the band itself had broken up.