The Toronto Maple Leafs acquired forward Phil Kessel from Boston on Friday night in exchange for three draft picks and signed him to a five-year contract worth $27 million US.
The Bruins are to receive first- and second-round NHL picks in 2010, as well as a first-rounder in 2011.
"It's a very high price but it's one that we feel makes sense for us," said Toronto general manager Brian Burke.
"Phil's a dynamic player, I've had him with the U.S. national team," Burke added. "He's got great foot speed, he's a good power-play specialist, he's good on the shootout and he's a solid kid.
"For us, it's an important day for the Leafs, and we're very pleased that Phil Kessel's coming to Toronto [Saturday]."
The Maple Leafs have been pursuing Kessel for more than three months, with Boston pressed against the salary cap in its bid to re-sign the restricted free agent, who turns 22 next month.
Allison shows off old tricks
Kessel's arrival will eventually mean one less available roster spot, but comebacking Jason Allison is giving it a shot.
Allison, out of the NHL since 2005-06, set up two goals as Toronto came back from a two-goal deficit Friday for a 4-3 win in Pittsburgh.
Jason Blake, Ian White, John Mitchell and young Slovakian defender Juraj Mikus scored for the Leafs. James Reimer and Joey McDonald split netminding duties.
Superstar Evgeni Malkin was among the goal scorers for the Penguins.
Kessel, who is on the mend from a shoulder injury and won't be ready for the start of the regular season, posted career highs of 36 goals and 24 assists in 2008-09.
The Madison, Wis., native was selected fifth overall by the Bruins in the 2006 NHL entry draft and overcame testicular cancer in his rookie season.
The Leafs have been linked to Kessel since June. A rumoured deal that would have involved veteran Toronto defenceman Tomas Kaberle never materialized, and when Toronto required the last needed draft pick to sign Kessel to an offer sheet earlier this month, speculation ramped up again.
Boston's ability to re-sign Kessel was also made difficult by friction between general manager Peter Chiarelli and Wade Arnott, Kessel's agent, with the grievances being aired publicly by both sides.
Burke said the three draft picks were made slightly more palatable by the fact that the Maple Leafs have signed a number of free agents from Europe and the U.S. college ranks in the past year, including goalie Jonas Gustavsson and forward Tyler Bozak.
Burke would not confirm the reported numbers, but said it was a multi-year deal.
Chiarelli is expected to address the media Saturday morning in Boston.