The ultimate addition by subtraction.
Can both teams be correct in their assessments of this blockbuster deal?
It will be easier to determine the early returns from the Pittsburgh side of the equation.
Kessel is durable -- he has not missed a game since becoming a Leaf in November 2009 -- and has been a consistent goal and point producer. Since coming to Toronto, he is fourth in goals and 12th in points among all NHL players.
But -- and this is a "but" that might well be written in bold capital letters with neon lights blinking around the edges -- there are issues that will continue to dog Kessel in his new home, including his tepid finish last season when he scored just twice in his last 21 games.
After Randy Carlyle was fired in Toronto, the entire team laid down, but Kessel, allegedly part of the team’s leadership core, was nowhere to be seen. And there were a number of angry encounters with local media in Toronto.
When Toronto president Brendan Shanahan took over the team and promised change to the team’s culture, everyone looked at Kessel.
Now that change has been made.
Will it be a catalyst to meaningful and positive change in the Leafs dressing room?
Certainly the Leafs' return on the Kessel deal is all about the future -- prospects Kasperi Kapanen and Scott Harrington, and a first-round and third-round pick in the 2016 draft -- and it speaks to the long road to recovery for a team that might have hit its low point in the more than five decades since its last Stanley Cup.
Nick Spaling also goes from Pittsburgh to Toronto, while the Penguins get oft-moved defenseman Tim Erixon and Tyler Biggs, both of whom are former first-round picks, and a second-round pick in next June’s draft.
The Leafs, meanwhile, will retain 15 percent of Kessel’s salary or $1.2 million annually -- a big boost for the cap-challenged Penguins.
It’s easy to see why Kessel, 27, became a lightning rod for the significant discontent that surrounded the Leafs in recent years, but especially last season when an embarrassing stretch of hockey caused the Leafs to miss the playoffs for the ninth time in 10 years.
Kessel is shy at best with the media and so his shyness can easily be misconstrued as indifference or churlishness.
Unless of course he really is indifferent and churlish by nature.
The reality may lie somewhere in between.
Does it matter to Pittsburgh head coach Mike Johnston or the rest of the team?
Not if Kessel scores 45 or 50 goals and leads the Penguins on the playoff run that has eluded them since going to back-to-back Stanley Cup finals in 2008 and 2009.
Is that likely?
With the Penguins' bottom six forwards still an unformed mass and the defense a work in progress, with Paul Martin and Christian Ehrhoff (presumably) departing via free agency, and with key players Olli Maatta and Kris Letang both coming off serious health issues, nothing is a given.
What is certain, churlishness or not, bad attitude or not, is that Phil Kessel is a goal-scoring machine and he’s going to play with either Crosby or Malkin (or both), and that dynamic should produce fireworks worthy of the Fourth of July.
It’ll take longer to find out if Kessel really was a drag on the Leafs’ evolution, but we’ll find out pretty quickly whether he can be a catalyst to newfound greatness in Pittsburgh.
Either way, we’ve not heard the last of this fascinating deal and who may ultimately come out ahead as a result of this blockbuster and social experiment.