The NHL first started recording power-play and penalty-kill opportunities during the 1963-64 season. With Toronto's partial season called out, the 10 worst teams since then have been:
| Year | Team | PK% |
| 2009-10 | Toronto Maple Leafs | 68.32 |
| 1979-80 | Los Angeles Kings | 67.7 |
| 1982-83 | Los Angeles Kings | 68.24 |
| 1978-79 | Washington Capitals | 70.25 |
| 1984-85 | Vancouver Canucks | 70.53 |
| 1978-79 | Colorado Rockies | 70.62 |
| 1981-82 | Los Angeles Kings | 71.29 |
| 1974-75 | Washington Capitals | 71.34 |
| 1985-86 | Los Angeles Kings | 71.7 |
| 1977-78 | Vancouver Canucks | 71.74 |
There's a lot of repetition there: the very bad Kings teams of the early 1980s; some equally-awful Canucks and Capitals teams; and the Rockies team that was so bad somebody thought it would be a good idea to hire Don Cherry to coach the next season. And almost all of these seasons occurred during a period of high-scoring and talent dilution. What if we look at how team penalty-kills did relative to the league penalty-killing average?
| Year | Team | PCT AVG |
| 2009-10 | Toronto Maple Leafs | -16.1 |
| 1979-80 | Los Angeles Kings | -13.4 |
| 1982-83 | Los Angeles Kings | -11.5 |
| 1974-75 | Washington Capitals | -10.5 |
| 1993-94 | Ottawa Senators | -9.9 |
| 1984-85 | Vancouver Canucks | -9.3 |
| 1978-79 | Washington Capitals | -9.1 |
| 1970-71 | Vancouver Canucks | -9.1 |
| 1977-78 | Vancouver Canucks | -9.0 |
| 1976-77 | Minnesota North Stars | -9.0 |
The list doesn't move around that much - we get a few more bad teams from the talent dilution era, a brutal 2nd-season Senators team...And your 2009-2010 Toronto Maple Leafs.
No matter how you slice it, this year's Leafs take is historically bad on the power-play. Every single player with regular PK time other than Jeff Finger has given up goals at a rate that's worse than the league-average. Mike Komisarek, Nikolai Kulemin, Wayne Primeau and Francois Beauchemin have been particularly bad, allowing goals at double the NHL average, or worse. Komisarek's poor PK work is made even worse because he did not even play against top PP lines at 4-on-5. And let's not forget Vesa Toskala, who has had a humiliating 768 save percentage down a man - that's so bad that it can't all be the fault of the skaters in front of him.
I'm not sure there was any way to predict that the Leafs PK would be so bad. They were awful last year, but they brought in several defensemen who've had success killing penalties in the past, along with a better goaltender. And yet they went a bit in the wrong direction. It's hard to be this bad for any length of time, so expect them to improve to something other than an historic failure in the future. And remember that it could always have been worse: the Minnesota Wild went from having the best penalty-kill in 2008-09 to 28th in the league this season.