Doc Rivers has never seemed like the kind of coach who is afraid to speak his mind. From candid between-quarter interviews (the same interviews that Greg Popovich uses to become an unholy terror to sideline reporters) to on-court interaction, Doc seems to be the kind of person who lets you know where you stand. Sounds like the kind of person you’d want to have coaching an underachieving team, doesn’t it?From the sound of things, Jeff Green is not being spared from Doc’s tough-love motivation. From WEEI’s excellent Celtics blog Green Street:“Jeff is important to us, not [just] for this year but for long term. I’m hard on Jeff,” Rivers said, clearly referring to the $36 million investment through the 2015-16 season.Then Rivers thought pattern changed on the fly, almost as if he was catching himself lowering expectations of the swingman who was just given a four-year commitment from the team after proving himself healthy after heart surgery last January.“I don’t actually think I’m hard on him. I think I’m fair on him,” Rivers said. “I think he’s hard on me. So, we’re going to demand out of him this year to be great because I think he has the ability to be great.”That about sums things up perfectly. Green is too talented to let slip away via free agency, but he hasn’t performed at a level that warrants the contract he was given. What’s the best way to handle a catch-22 like that? By paying the man, then by being hard on him until either he accomplishes his potential or you are quite certain that he will never reach it, at which point you part ways.It should be noted that Doc is also fantastic at personnel management. He is very good at convincing players to buy in and drink his kool-aid, but he also knows where to draw the line with each player. So while these quotes sound pretty rough on Green, rest assured that Doc knows exactly what he’s doing, exactly how far to go, and exactly which ways to poke and prod Boston’s backup forward.Basically, if anybody in the NBA can get an underachieving, long, athletic stretch forward to turn into a regular contributor on a title contender, Doc Rivers would be my first choice. And Greg Popovich would probably be my second, unholy sideline reporter terrorization and all.Follow Tom on Twitter: @Tom_NBA.