Diesel was the ex-boyfriend of Nikki Witt. He was in a rock band called Diesel Stone and the Waste Management and came back into contact with Nikki while she was attending a performance with boyfriend Brandon Walsh of David Silver, who blew his performance much to Diesel's amusement.
Diesel was abusive to Nikki in the past and the reason for her leaving San Francisco. When Diesel began to weasel his way back into Nikki's life, Brandon felt like he was losing Nikki to her past. However, when Diesel's old habit of taking out his aggression on Nikki returned, Brandon stepped in and knocked Diesel out with one punch. Nikki later returned home since Diesel was then out of her life.