Doc Rivers was disparaged as a coach who couldn't get a system in place or get productivity out of the Celtics before the current "Big 3" was assembled in the summer of 2007. Now he is seen as more of a veteran's coach who gets peak performance out of a unit where egos could easily dominate and cause diversity.
I'm going to say he's largely the same person he was before and after the 2008 season. So what gives? Well, contrast that to Avery Johnson, who is a control oriented coach with seemingly perfect technical knowledge and attention to detail. He also oversaw two of the biggest choke jobs in NBA history, squandering a 2-0 lead in the NBA Finals to a Miami Heat team that only won 52 games that year (compared to Dallas' sixty games). The following year, his 67 win team (67!!!) lost to the Golden State Warriors who squeaked into the playoffs on the final day of the regular season, before promptly losing 4-1 to Utah, who lost 4-1 to the Spurs, who finally won the championship.
Meanwhile, Doc Rivers lead a team with a solid starting five to upset victories over the league leading Cavaliers (61 wins) and then the Magic (59 wins) and nearly beat the Lakers, narrowly losing a game 7 in which the lead by 13 points in the third quarter.
Whats the difference? How can one coach who is able to pound and mold a team into a well-oiled regular season machine able to choke in the playoffs while coach Doc Rivers stumbles through home losses to the Nets and Wizards only to pull a five headed rabbit out of the proverbial hat once the playoffs start?
I don't know. I doubt anyone does. But consider a quote from Doc Rivers who said, and I quote "I'm a typical guy. I can point out the problem but I don't have a solution". It takes a big man to say that. Avery Johnson would never say that. Ever.