Carter Verhaeghe
The Islanders aren't the only team who wish they could have Carter Verhaeghe back, as the Toronto Maple Leafs and Tampa Bay Lightning are also surely regretting letting go of a 40-goal scorer. Though he never suited up for the Islanders, the current team could desperately use a player with his scoring prowess. Acquired from the Leafs in 2017 as one of five players sent to the Islanders for Michael Grabner, Verhaeghe was a former third-round pick who struggled to get going in the AHL.
After two years of bouncing between the AHL and ECHL, GM Garth Snow shipped Verhaeghe to Tampa for goaltending depth in Krister Gudlevskis. Gudlevskis spent only one season in Bridgeport before heading to Europe, where he's remained ever since. Verhaeghe, now a member of the Florida Panthers, was the leading goal scorer (42) on a team that made it to the Stanley Cup Finals. His nose for goal and team-friendly contract could be the missing piece for the Islanders' current roster, but it was nearly impossible to know the type of player he'd eventually become.