New York Islanders
Kyle Palmieri is the only player I could see the Leafs targeting from the Islanders. I doubt the Islanders will move him, but if they are willing to trade him, Palmieri would be a good depth player for the Leafs.
He has 13 goals and 15 assists for 28 points in 49 games this season. Palmieri is averaging 16:58 minutes of ice time with a Corsi For percentage of 49.4%, along with 39 hits and 27 blocked shots.
The 33-year-old Palmieri has 63 games of NHL playoff experience. He has registered 17 goals and 12 assists for 29 playoff points. Adding Palmieri as depth and added leadership would not only be for this season. He has another season after this one with a $5 million salary cap hit. The Leafs will need to move another player out if they hope to add Palmieri at full cost.
The only other player I could see the Leafs wanting from the Islanders would be Matt Martin, but he is not an upgrade over any of the players we have now.
He plays the same role as Ryan Reaves, and the Leafs will find it hard to move Reaves, but most of his cap hit can come off the books if he's sent to the Marlies.