Was Pittman leaving early really a surprise? If I recall part of the equation was his family needing the money. Regardless, I'm not sure Pittman's situation ties into Grant's or Apple's. Grant's for the obvious reason of being a senior. Him being cut was a bit shocking, usually 4th rounders still make the squad. It's still not a death sentence. How many times was Kurt Warner cut? Just saying.
With Pittman, I think he was doomed from the start. Drafted by a Saints team that already had Deuce McAllister and Reggie Bush, so that didn't leave many options for Pittman. It's no surprise he was cut. By that time, many teams have their backfields set and he was at the mercy of whoever looked like the best option for playing time.
I think Apple most closely resembles Chimdi Chekwa. It certainly appears Apple has a higher draft projection, but I remember talk of Chekwa leaving after '09 and how he'd benefit from another year of seasoning. I think that's where Apple is. He'd no doubt get drafted, but how high? Maybe coming back another year and proving any question marks gets him the BIG bucks.