All of the Big 3 declined.
But none as much as Tony Parker. He went from being a top 3 PG and in the top 10 PER to not even making it the top 50 PER this year for the regular season. Tim Duncan finished 5th overall and Ginobili finished 12th in the regular season. For the playoffs, Tim Duncan was 25th and Ginobili, 15th. Parker finished at no. 43. Parker was 2nd last year in playoffs PER and Duncan was 4th in that short series against the Mavs.
Yes, he's had injuries but its not like Duncan isn't dealing with a degenerative knee condition or that Manu's nose wasn't broken. But Parker also had the most difficulty of the big 3 trying to incorporate the new players and unlike Manu...he's likely going to play for France to make things worse for this injury plagued core. Manu has shown the capability of running the team with Parker out and the best wins of the regular season came when Parker was sidelined.
Reasons for trading Parker:
1. Most valuable trading asset the Spurs have outside of RJ and Tiago's rights
2. Parker's not a leader even though he's the PG. Spurs have won against the top teams without him and Manu has really taken the role of being a vocal leader and helping guys like Blair fit into the Spurs.
3. Parker will likely play for France this summer while Manu rests. Next year is going to be one of the best shots the Spurs have with a rested Manu and Tim. Parker is far from healthy and far from what he used to be athletically yet he's going to get even more wear and tear.
4. Declined mightily. Didn't even finish the regular season as a top 50 player in PER which he used to finish in the top 10. Manu still finished 11th in his injury shortened season last year. Doesn't have the intangibles that Manu and Duncan have either to make up for the lack of boxscore stats.
5. This will be the biggest offseason in recent NBA history. Teams are going to be losing their star players and needing to revamp their rosters so there will likely be opportunities to gamble on.
Of course there has to be a deal worth a damn.