David Boies is known for juggling high-profile cases. This fall, for example, he is handling a divorce that could decide the ownership of the Los Angeles Dodgers while also preparing for trial in a $3.9 billion dispute pitting client Terra Firma against Citigroup Inc.

But according to one disgruntled former client, while Mr. Boies attended to other major cases he neglected to perform his lead counsel duties in a more mundane commercial dispute in Nevada federal court that was scheduled for trial in September.