As badly as the Suns were screwed by the NBA and as important as Amare Stoudemire and Boris Diaw are to the team, Steve Nash Shawn Marion and Leandro Barbosa are still there, so Game 5 is NOT a lost cause. In the absence of Stoudemire and Diaw, the Suns do not need to change their gameplan, but they will need to make some adjustments.
Offensively, they will need to get Shawn Marion involved early. He is the most versatile player on the floor, able to create his own shot off the dribble, fill the lane on the break and hit from the outside. Marion is the player on the Suns most capable of getting the Spurs into foul trouble, which would be huge in filling the void created by the suspensions. Also, if Marion gets going early, all of the Spurs will need to pay attention to him on defense, open up driving lanes for Nash and Leandro Barbosa, and creating open looks for Raja Bell and James Jones.
Defensively, the Suns, without a true shot-blocker in the paint, will need to stay at home on San Antonio's perimeter players and not allow Parker, Ginobili and Finley to drove to the basket. Phoenix will have to guard Duncan straight-up and risk him having a monster game. This way they can limit the Spurs' open looks from the outside, not allow easy drives to the basket avoid mismatches on the boards.
With the talent still on the Phoenix roster for Game 5, not to mention a crowd that will be in an absolute frenzy, this game will be very competitive. As long as the Suns can keep Kurt Thomas and Shawn Marion out of foul trouble, they have an excellent chance of pulling this game out. It is important to remember, after all, that the best player in the series will be on the floor for the Suns. If it's close in the fourth quarter, look for Steve Nash to will the Suns to the victory.