David Quinn had a hard time with this particular benching

Brendan Smith NHLI via Getty ImagesIt was easy to see the difficulty of the decision drawn on David Quinn’s face.

But it was one the Rangers coach felt he had to make, scratching defenseman Brendan Smith for Wednesday night’s 5-0 thumping of the Islanders at the Garden. It was the fourth time in the past six games that Smith has been scratched, but it was the first time Quinn had to scratch someone that he didn’t think deserved it.

“Really the first time this year that a guy is sitting that shouldn’t be,” Quinn said before be brought Brady Skjei back into the lineup after his two-game sojourn in street clothes. “But as I’ve talked about, we really feel like we have eight defensemen that can…