Exclusive: Sullivan reveals key problem metric for Penguins

NHL teams accumulate a lot of statistics, from the most traditional to the latest in advanced analytics, over the course of a season.

The Penguins are no exception, and they can find something of value -- or, at least, of interest -- in pretty much every one of those numbers.

But when Mike Sullivan assessed his team's performance in 2018-19, there was one figure he felt captured the essence of why the Penguins did not qualify for the Stanley Cup playoffs until the waning days of the regular season, then lasted only a week after they got in.

"We were 31st in the league in odd-man rushes against," Sullivan said. "I shared this conversation with a lot of our top guys and our coaching staff, and I…