1:8 "The Admiral" David Robinson.
The 2nd of the Twin Towers. Is there any denying their greatness?
Robinson entered the league at 24 and immediately made an impact. He was chosen for the All-Star team, 2nd All Defense team, 3rd All NBA team, and was named Rookie of the Year. He would be An All-Star every year from 1990 to 2001, except the year of his freak broken foot in 1997. He won two NBA finals, was the MVP in 1995. But you know all of this, right?
The biggest reason David Robinson is underrated is because people just don't agree how high his peak was. Robinson lead the league in PER three years running: 93-94, 94-95, and 95-96. His PER during this time was over 29. The only two people of this era to have a higher peak are Shaq and Jordan.
But even if you don't like PER, during this time he actually had a scoring title (with close to 30 pts per game), was all defensive twice, and all NBA twice. He averaged 27/11, shot for about 52% and got to the line 11 times per game. Robinson also converted on over 75% of his free throws.
Win Shares? Robinson lead the league the first two years, and the only reason his 53 win shares weren't #1 in 95-96 was because Michael Jordan came back and had 57. The only thing that stopped Robinson's utter dominance were back problems and a freak broken foot injury the following year. Yet, Robinson was ridiculously healthy the rest of his career. And like Duncan, Robinson's dominance came on defense. Robinson lead the league in defensive rating 5 times and has the third best defensive rating in the era, behind only Duncan and Ben Wallace. He lead the league in defensive Win Shares 4 times and is 3rd, behind only Hakeem and Karl Malone - despite playing many less games than they did.
The only problem with Robinson's career was that it was too short. However, pretty much all of that comes from the fact that he started at 24 and missed his age 29 season. Neither of these should be a problem in this league.