Since it's football season, we'll probably be seeing this sketch on Late Show with David Letterman again.
Here, Dave "interviews" someone who looks exactly like the head coach of the 49ers "via satellite" (he is probably standing just off-camera). The mock-Singletary spouts non-sequiters which are audibly being fed to him from a staff member.
Like a lot of Letterman's sillier bits - this is mostly funny only because he insists on repeatedly doing it.