The Leafs have more than enough players to set up a proper penalty killing unit. The fact they ended the season below NHL average is concerning when coupled with the team's year-to-year decline (though that can be explained by the annual league-wide decline in PK efficiency). However, considering that the most prominent issue, the lack of a center that could take the draws, could have been addressed by up to three players on the roster - Tavares, Kadri, and Gauthier - was never experimented throughout the year is puzzling. First guy has played on NHL PK units, the other was surprisingly productive killing penalties in junior, and the last is an under-played defensive specialist. The coach is willing to take a chance with speedy wingers on the PK, but is reluctant in putting round pegs into round holes? I liked the development angle taken with Marner but if that were truly the case, then even Matthews was also available to satisfy the requirement for a center with the added benefit of providing him with experience.
It's hard to find any logic for how the PK was manned and depending on how one looks at it, the lack of calls against us this year was either a blessing or a curse. A tougher lineup will crumble with a weak PK unit supporting them.