Could it be because Rivers' Celtics got the better of Jackson's Lakers in 2008? Or could it be because Rivers had to adopt a Jacksonian long-view approach to coaching this season? Then again, maybe it's because they're in the same situation: that for all that they've done to get their teams to this point, there's no guarantee either of them will be back with his team next season.
Finality is normally a term associated with players. This could be the last hurrah for Boston's Big Three, and as obsessed as Kobe Bryant is there's no guarantee he'll ever get this close to the Larry O'Brien Trophy again. For coaches, a trip to the Finals is usually the best form of job security.
Teams on this grand stage aren't supposed to join the basement-dwellers such as the Nets and Clippers in the coaching market after the series is done. It could happen this year, though. The Lakers don't want to keep paying Jackson the $12 million he made this season, and he has balked at taking a pay cut. Rivers, as the Boston Herald reported in April, is considering walking away from the final year of his contract that pays an average of $5.3 million annually to watch his kids finish out their collegiate and high school athletic careers.
"It's interesting both ways," Rivers said. "Both of us have our own reasons, but I don't think either one of us think about it. I don't think about it at all."
He doesn't publicly weigh the pros and cons in front of the media. He doesn't talk about it with Celtics general manager Danny Ainge.
"I won't even talk it over with my family," Rivers said.
For the moment, there's no decision to discuss.
"Doc doesn't know," said a person close to Rivers.
"Doc's unpredictable. He cares about his kids. He's saved lot of money. He can afford to do what he wants to do."
Jackson has been making more than double Rivers' salary, even after Doc got a raise in 2008. Jackson could head off to his cabin in Montana. He could go to the Nets and sip vodka with Mikhail Prokhorov as they gaze at the Hudson River. He could try to do for LeBron James what he did for Michael Jordan and Kobe Bryant.
And he isn't uncomfortable addressing any of the possibilities, even a scant 80 minutes before the start of a playoff game, his news conferences becoming entertaining jousting with the media as he refutes some possibilities, stokes others and uses the sessions as a negotiating ploy that even Rivers has come to admire.
"He's become pretty good," Rivers said. "I'm not like that. You know how I am; I just try to leave it on the side."
Yes, their styles are different, and the primary distinction is in the way Jackson is so proactive with his public statements about his own future, to sway the officials, play mind games with opponents or even motivate his own players.
"Phil always has that ulterior motive, that hidden message," said Will Perdue, who played on Jackson's first three-peat teams in Chicago and was Rivers' teammate on the San Antonio Spurs. "I think 90 percent of the time the players never figure it out. He guides them without them even knowing.
"Doc is very to the point, very blatant, very honest. 'This is what I need you to do, this is what your responsibility is, this is how you do it.' Some coaches can't pull that off, because they either didn't play or they don't have the respect of the players or whatever reason.'"
Perdue points to Jackson's comments about Ron Artest taking too many 3-pointers early in the playoffs, which caused Artest to complain on Twitter that Jackson hadn't spoken to him privately about the issue first. But what happened after two days of a minor media flareup? Artest produced his best game of the playoffs to that point, scoring 20 points in the Lakers' victory over the Utah Jazz in Game 3 of the Western Conference semifinals. Another subliminal success for Jackson.
Rivers doesn't have to operate that way.
"Everybody here, we're at the stage where we kind of patrol ourselves, so Doc doesn't have to do a lot of worrying about it," Ray Allen said. "He can throw the X's and O's out there, tell us what to do, how we're going to do it, and everybody can do their job."
But the Celtics never would have made it this far if Rivers hadn't adjusted his style, taken the focus off the games at hand, loosened his grip on the steering wheel and looked far down the road to the playoffs. With Kevin Garnett and Paul Pierce nursing injuries through the middle of the season, Rivers had to sacrifice games.
"Our thought was, 'OK, we're not winning the East,'" Rivers said. "'We're not getting second seed, either. Third seed doesn't matter as far as we're concerned, so let's get healthy, let's get right.'"
That's not the way he came up. He won coach of the year his first season on the bench in Orlando by squeezing the max out of the regular season for a team that didn't even go to the playoffs. Jackson was the guy who never minded a short-term hit for a long-term payoff. He could leave a star on the bench even with the crowd screaming for his return, or let a feud simmer without intervening until the combatants realized they were dependent on each other. Coaches with multiple championships have that luxury.
For Rivers, it was a challenge just to get over the anxiety.
"It goes against every instinct you have," he said. "When a team's making a run in the middle of the game and you've got Kevin sitting on the bench and you know he should be back in and he knows he should be in and you're still sitting him, there's nothing smart about that at the time.
"As competitive as we all are, it was very difficult. It's not like it was brilliant, because it was the only thing we had, as far as I was concerned. We'd proven we were not going to win injured. You saw that model [in 2009], and that model didn't work. For us it was a simple decision."
And the right choice, as the Celtics found their stride in the playoffs -- just like Jackson's Lakers. And while the primary stories are the restoration of Bryant to the top of the game and the emergence of Rajon Rondo, neither team would be here without its coaching staff.
Jackson's old nemesis, Bulls general manager Jerry Krause, once told him that some guys do a great job with a 20-win team and some guys do an average job with a 50-win team.
"Kind of taking me down a step or two, so I wasn't too full of myself," Jackson said.
But the great coaches deliver championships, and no coach has won more than Jackson's 10.
"When you have a team that's in this position and you're in position to win, this is the pressure time for trying to get production out of your team," Jackson said.
His own uncertainty hasn't distracted the Lakers from their task. Nor has Jackson made as big a production about it as he did in 1998, when he labeled the Bulls' final three-peat run "The Last Dance." He hasn't used it as a motivational tool the way he did when the Lakers fell behind the Spurs 2-0 in the conference semis in 2004 and Jackson went around the room pointing out everyone who wasn't guaranteed to be back the next season -- including himself -- and urged them to fight to extend the group's time together.
In addition to Jackson's statements that he'll be with the Lakers if he coaches anywhere next season, there are behind-the-scenes indications that he could be back, including his involvement with planning for the team's summer transactions and its preseason trip to Spain next year. But there have yet to be any indications from the owner's office that Jackson's asking price will be met.
So all that's left for Jackson and Rivers is to play for a spot in history with no guarantee that it will have any bearing on their future.