Looking at it from a purely basketball perspective, the Knicks could still use some extra depth on the wing, especially considering the injury that will keep Iman Shumpert out until at least January.
Ronnie Brewer was signed to cover for Shumpert until then, but even he will miss the bulk of the preseason with injury, and this should send a warning to the Knicks that they don't have quite enough depth.
Considering his ability to play as both a shooting guard and small forward, McGrady could be that extra body the Knicks need, and would act as insurance if Brewer or J.R. Smith was to miss time during the regular season.
As a small forward, McGrady could also prove himself more useful than say James White, at the very least, and he may actually end up as the most well-rounded forward on the Knicks' bench if signed.
Steve Novak will obviously be used as a three-point shooter, but if the Knicks are also looking for someone to provide a bit more than that behind Carmelo Anthony, T-Mac could be their man.