In Kessel's first year with the Leafs, he played in 70 games, putting up 30 goals and 25 assists. The Leafs missed the playoffs and the 2010 1st round pick they traded ended up being the second overall pick, which the Bruins used to draft Tyler Seguin. Seguin won a Cup with the Bruins in 2011. The 2011 first rounder ended up being another top-10 pick, which the Bruins used to select Dougie Hamilton 9th overall.
As Kessel's tenure went on with the Maple Leafs, he became the scapegoat as the team struggled in the dressing room and on the ice. Kessel would be traded to the Pittsburgh Penguins in the summer of 2015 after playing six seasons in Toronto. Kessel led the team in scoring five times with four 30-goal seasons. He played in 446 games as a Leaf.
Kessel would get the last laugh though, as he won back-to-back Stanley Cups with Pittsburgh in 2016 and 2017. 13 years later, the trade still stings, but without this ill-timed deal, the Buds likely never draft Auston Matthews or Mitch Marner, so I suppose it's not all bad.