The Spurs' front office has been active this summer, but one of their most underrated moves was signing Billy Donovan as their lead assistant head coach. Billy Donovan brings a ton of experience to San Antonio's bench. As an NBA coach, he split time between Oklahoma City and Chicago, leading the Thunder to a 243-157 record and a run to the 2016 Western Conference Finals. There were some questions about how the Spurs would recover after losing Sean Sweeney earlier this offseason, but signing Billy Donovan seems like the perfect response. It's clear that they're serious about winning a championship, and Billy Donovan hopping on board is proof of that.