[From the Diaries. Lets not turn this into another mind-numbing argument over what makes a 'superstar'...the point is, for any offseason move to make much of an impact, these 3 guys have to get better as well. History shows they will, but by how much and how they fit is the more important question. Now that's something to argue (sorry, 'discuss') over. -Matt]
All of the recent debate over Kirk, Lu and BG's potential for improvement, not to mention over the term "superstar," piqued my curiosity as to what level of improvement other well-known players have experienced at a similar career stage as the core guys are at now. I do not in any way purport that this is a serious scientific study - just my quick perusal of stats found at http://www.basketball-reference.com/players/.
This is the average change in PER for eleven players at each position who have been in the league longer than Hinrich/Deng/Gordon from their season just completed to the one they are about to enter, so 4th-5th for point guards and 3rd-4th for SGs and SFs. No, PER is not perfect, but it is available and it controls for variations in minutes played. As far as selecting which players to look at, I took the top eleven guys that had been in the league long enough from a fantasy basketball preview list for last year - it was convenient. (Obviously this does not mean Hinrich/Deng/Gordon will not do better or worse than the average next year.)
PG - average PER increase of 2.927 from 4th to 5th year
SG - average PER increase of 1.091 from 3rd to 4th year
SF - average PER increase of .709 from 3rd to 4th year
PGs included, with individual increases from high to low: Nash (+6.1), Kidd (+6.1), Iverson (+4.0), B Davis (+3.8), A Miller (+3.7), Billups (+3.5), Parker (+2.8), Bibby (+2.7), Arenas (+2.5), Marbury (-1.0), Terry (-2.0)
SGs included, with individual increases from high to low: McGrady (+4.9), R Bell (+4.8), Bryant (+2.8), J Richardson (+2.2), Allen (+1.7), Wade (+1.3), Ginobili (+0.1), Pierce (0), J Johnson (-0.2), Redd (-1.1), Carter (-4.5)
SFs included, with individual increases from high to low: G Wallace (+3.5), Kirilenko (+1.8), Artest (+1.8), Marion (+1.5), R Lewis (+1.2), Butler (+1.2), Odom (+0.9), Stojakovic (+0.9), Anthony (+0.1), R Jefferson (-1.5), James (-3.6).
I didn't do any analysis for significance, but I thought the PG numbers were especially interesting - with the exceptions of Marbury and Terry, all of those guys had a significant jump in PER in the 5th year. This would definitely seem to support the idea that point guards make significant improvements at a later time in their careers, and possibly bodes well for Kirk (and consequently us!) next year.
(Just to be clear, I did not look at changes over other years, did not consider moves to other teams or changes in teammates or coaches or playing time, and did not take the time to look up injuries.)