[Assani Fisher]

I'm not sure if this counts since I don't think hes underrated for what he did in the NBA. But many people don't realize how good Arvydas Sabonis really was in his prime before coming to the NBA. I've heard him described as "Shaq with the ability to pass like Magic." Many believe he would've gone down as one of the best centers ever if he had been able to legally come to the NBA earlier.

From wikipedia:

In between rehab stints, "Sabas" would find himself out on the court playing pickup games with Clyde Drexler, Terry Porter and others. Observers strongly contend even to this day, that had Sabonis played for the Blazers in the early 1990s, they would likely have won a NBA championship


In 1995, he finally joined the NBA with the Trail Blazers, and won Rookie of the Month and Player of the Week awards in 1996. He was later runner-up for both the Rookie of the Year and Sixth Man awards. He remained with Portland for seven years, playing in 470 regular season and 51 playoff matches with them and often leading the team in rebounds. He was a very effective player in the NBA, and was named European Player of the Year twice while in Portland, but his career there had considerable "what-might-have-been" overtones. Had he joined the Blazers when they were at their peak in the early 1990s, many Portland fans feel it would have been a dynasty. During his years in Europe, he suffered a series of knee and Achilles' tendon injuries that robbed him of most of his mobility.



Ex-players and current players alike contend that Sabonis, fairly unknown in the U.S., would have been recognized as one of the top centers ever to play the game of basketball had he come to America in his prime. Scottie Pippen was quoted as saying that Arvydas was "the best European basketball player to ever play the game". Ex-Spur Sean Elliott routinely claimed that Arvydas "should be in the conversation as one of the greatest centers ever". Hall of Famer Bill Walton describes "Sabas" as "the greatest passing center of all time". And Dino Radja, a former Boston Celtics player, said that Sabonis would have been an all-star "ten times over" had he played his healthy years in the States.

Brian Meehan, a columnist for The Oregonian, followed Sabonis' career over the course of decades. Recalling the 1988 Olympics, when Sabonis' Soviet team beat a United States team with the likes of David Robinson, Meehan notes one play when a healthy Sabonis reacted to a teammate's missed shot: Sabonis slashed towards the rim, jumped over Robinson, and slammed the ball home. Meehan is of the opinion that it was the play of Arvydas in the '88 Olympics that influenced Team USA to use professional players in the Olympics, thus the "Dream Teams" of 1992 and 1996. Meehan ranks Sabonis as the 6th best all-time center behind, in no particular order, Hakeem Olajuwon, Bill Russell, Wilt Chamberlain, Shaquille O'Neal, and Kareem Abdul-Jabbar.