The Penguins have absorbed 215 hits from Columbus in the first four games of their opening-round playoff series.

That’s easily the most of any NHL team in these playoffs, and that total doesn’t even include the one their own coach delivered Thursday.

Dan Bylsma, asked what aspect of his team’s performance in Games 1 through 4 troubles him most, did not point to the Penguins’ penalty-killing, which has dropped from 85 percent efficiency to 75 percent against the Blue Jackets.

He didn’t mention that Brooks Orpik and Craig Adams, who combined for seven goals in the regular season, have one each in the series. Which means they each have one more than franchise centers Sidney Crosby and Evgeni Malkin. Combined.

In fact, Bylsma didn’t bring up anything rooted in simple statistics. Instead, he cited a far more fundamental concern.

“The work and the compete and the battle level has probably been the most troubling thing from our team,” he said.

“That’s been the thing throughout this series, to this point, that’s been most troubling. It’s got to be raised.

“It’s got to be back up to a level that is necessary at this time of year, and in this type of hockey. In playoff hockey.”

That shortcoming hasn’t been a constant — there have been times when the Penguins have dominated, and when they’ve overcome major adversity — but it’s happened often enough that they are tied, 2-2, with a team that was a near-prohibitive underdog going into the series.

And Game 4, when the Penguins built a 3-0 lead in the first 12 minutes, only to lose, 4-3, in overtime Wednesday at Narionwide Arena, underscored what can happen when the Penguins allow their sweat glands to have a little down time.