Parker is 28 and had a bad year full of injuries. He is taking the summer off. Just last year he was carrying the team through the season. If you take the Parker Hate Glasses off, you will see that he has developed a pretty reliable midrange jumper. The "decline" you speak of is not age, it was simply plantar fasciatis, which is healed with rest. There is no reason to expect a decline with no serious knee injuries, etc. Manu is 32. The "championship Manu" that we all love can't play a whole season without some kind of injury, and unfortunately it always happens at the end of the year.
Yes, giving a player a max deal after an injury riddled season is risky, but what's more risky is giving Manu the deal he got. THAT contract has caused the problems, because now you have to give Tony AT LEAST that, because Tony is young and will be around longer than Manu. For the record, I don't think Tony is max contract player, but he deserves more than 10 million and at least as much as Manu.