Like that comeback no one wants to see happen, Ubisoft's always-on DRM is making an encore appearance for the PC version of Driver: San Francisco. Ergo, if you don't have an internet connection, or if Ubisoft's servers go down due to maintenance or hackers or Act of God(s), you can't play the game. Not even in single player (also known colloquially as "offline" mode).
Ubisoft's frustrating DRM preferences are nothing new. We were even foolish enough to believe that we were done with this nonsense a while back.
Oh and by the way, in case you wanted to play the game with a steering wheel, Ubisoft has confirmed via tweet that it's not happening.