While I don't believe they need to be calling isolations for him down the stretch, you're right. Manu and Tony seemed to forget about him (and most everyone else for a stretch there) during some crucial stretches -- the guy scored on the outlet to end regulation but I don't believe he took a shot for a good stretch before that play or even one in overtime.
What kills me about games like last night is when Manu tires and no one puts the onus on themselves to finish the job, or simply the fresher man doesn't demand the ball.
Manu had his shot going and he's always got the guts of a burglar. But when he doesn't have his legs to get to the cup, he starts getting 3 happy. And when Manu gets 3 happy, that ain't good for the team -- the Spurs need to get to the basket, and subsequently, the line, down the stretch. No one on the Spurs gets to the line easier than Manu when he's got his legs, but RJ has been getting there more frequently this year.
That's why they need to get RJ involved more late in games. They need to create the seams so RJ can attack off the ball to get to the line late. It's RJ, Manu and Indy that have gotten to the line most frequently this year and they need to know that for situations like last night.