Why did Doc Rivers shock the world (OK, that's a slight exaggeration) and decide to come back for another year as head coach of the Celtics? Here's the five best reasons I could come up with …

1. He may never have a better chance to win another title

Listen, the 2010-11 Celtics are going to have serious flaws. Of course it'll help if they bring back Ray Allen and Paul Pierce, but at best you're looking at an aging core (minus Rondo) that has seen its regular season win total drop each year since the 2008 title. It's easy to assume that the group that ran through the Eastern Conference playoffs will just show up again next year in April after taking the last three months off. Rested and ready to dominate again. Well, it doesn't usually happen that way. So just remember that if they bring back the whole band again. I still think that 27-27 stretch means something.

But if we take a glass is half full look at this it's easy to see why Doc is going to spend the great majority of next winter flying between Boston and Orlando. The 2010 Celtics had an easier route to the NBA Finals than the 2008 team. This is a team that won six straight playoff games against the two teams -- Cleveland and Orlando -- that were supposed to be the superpowers of the conference. They got to the Finals and had a 13-point lead in the second half of Game 7 in a series which no member of the team played well enough to really earn an MVP (think about it -- who would have won it had the Celtics hung on?) So it's not hard to figure out why the Celtics --provided everyone that really matters (sorry, Scal and Nate and maybe even Tony)-- think they have as good a chance as anyone to win next year. The "one last ride" deal makes sense if you're Doc. Why not? He could sit out five, six, seven years and maybe not find a team looking for a coach that is as close to a championship as this one. 

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2. He knows things that we don't (inside baseball)

I'm pretty sure Doc Rivers doesn't sign on for one more year (and maybe more) if he wasn't given assurances that Pierce and Allen (or some version of Allen, a MIke Miller/Anthony Morrow type)  will be back. I wonder if he isn't already aware of where the LeBron-Wade-Bosh trio end up and if that didn't play a factor in his decision. Maybe the idea of the three all on the same team would have swayed Doc to leave the bench. Who knows? But if that doesn't happen (and it seems increasingly likely that it won't) does a LeBron-Bosh duo scare you that much? The Celtics controlled the Cavaliers in that series a month ago. Does adding Chris Bosh -- who has never won a playoff series -- mean the difference? I'm not sure and I suspect Doc and Danny aren't either. And does Carlos Boozer or whatever B-lister the Heat will give Wade get them even close to a Celtics team that steamrolled them in the first round? Are any two players as good as the Boston "core four"? OK, Gasol and Bryant, but how about in the East?

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3. Loyalty

Hey, it's the answer Jerry Maguire gave Rod Tidwell when asked why he married Dorothy Boyd. You know that movie is 14 years old and I bet I've watched it 75 times, but I still can't figure out if Kelly Preston used a body double in that scene in the kitchen. Not even Google has helped me. One of the three great body double mysteries in movie history, along with Jamie Lee Curtis on the pole in "True Lies" and Ben Kingsley in "Gandhi" (all the surfing stuff and the 26-minute deleted sex scene with Linda Lavin, which is on the DVD).

But back to Doc. Listen, when the Celtics hired him in 2004 he had coached as many winning playoff series as M.L. Carr. We all knew him as a player and as TV guy, sure, but there was zero buzz was he was named coach of this team. The coach of the year at age 39 in 2000, his stock plummeted over the next three-plus years in Orlando. He came to Boston as little more than a retread, to be honest. And his record after three seasons with the Celtics was 102-144. Would have been easy for Danny and Wyc and whoever else has a voice to show Rivers the door. And you know what? I'm not sure Doc would have found a job again, at least not one that didn't involve Donald Sterling. One wipeout is forgivable in the NBA, but two coaching flops is usually a death sentence. So what did the Celtics do after 2007? Signed Doc to an extension. Now he proved to be worth it, of course, but he's doesn't get the chance if the Celtics brass didn't show loyalty. I have to think that was put in the "reasons to stay" category when Doc weighed his options over the past couple of weeks.

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4. "I told our guys this, the starting lineup still hasn't lost. I told them, you're still yet to have a true chance to defined your title."

That was Doc in the press conference after Game 7. That struck me at the time as the kind of words you don't hear from someone on his way out. And he's right, the Rondo-Allen-Perkins-Pierce-Garnett group is 7-0 when all are in the lineup for an entire playoff series. Not sure what that really means at this point -- aren't injuries part of the game?-- but Doc is sure sticking to it. And you know if they are all back and in the playoffs next year it'll be a big theme for Doc. 

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5. He probably just likes being head coach of the Celtics

Could it be that simple? Beats the hell out of coal mining, I would guess. These coaches never seem to leave, did you ever notice that? They'll make plenty of noise about it, take time to weight options, speak to family and friends, but they almost always come back. Can't just be the money, right? I don't know what it is, but maybe we'll figure it out before the whole "Will Doc stay or go" circus begins again in about a year. In the meantime keep the arm loose, Kevin McHale.