It's notable that when teams play with one defensemen on the power play, they can be prone to shorthanded goals. Forwards generally aren't as responsible defensively and if the defenseman pinches or carries the puck deep, it falls to a forward to guard the point. This can lead to odd-man rushes against a forward, or worse, guys going for line changes because they are used to having cover behind them. That's what happened in this game between the San Jose Sharks and Toronto Maple Leafs, a team that uses a strict 1-3-1 and generally plays with a lone defenseman at the point.
In something of a broken entry, Joffrey Lupul attempts to send the puck around the boards, but his attempt catches San Jose defenseman Brenden Dillon in the arm and doesn't get very far. Jake Gardiner, who had been watching from the blue line, races in to recover the puck, and follows Tommy Wingels down into the corner on the forecheck. Brent Burns sends the puck around the boards and out.
While this is happening, tired Leafs players have headed for a chance, but Peter Holland, as the last man back, stays just to make sure there isn't the potential for an odd-man rush. Once the puck is cleared out, though, he too heads off, thinking that Gardiner will come back and recover the puck to hand it off to the second unit. The problem, obviously, is that Gardiner has the same idea, believing Holland will take care of the puck, or that somebody will be able to jump onto the ice quickly enough to do so. Instead, Wingels and Matt Nieto alertly pounce on the puck, start a 2-on-0, and score on a helpless Jonathan Bernier.
The moral of the story? Being the point man on the power play is a big responsibility, one that shouldn't fall to just anybody. But being the default next man back is also critical, as is having awareness of your team's vulnerability due to your power play formation in the interest of generating goals, and playing responsibly when play demands it.