A solitary second half goal from Adam Taggart was enough to give the hosts a crucial victory and snap the Heart's five-match winning streak.
"We couldn't really play our game," declared van 't Schip.
"The circumstances were not really good. There was a lot of wind in the first half and the pitch was not in good condition so that makes it difficult to play it on the ground.
"In the air they were strong, they have Heskey up front and in the back they have Jaliens, Mitchell and Zadkovich that were heading a lot of balls away and winning a lot of their one on one's with high balls.
"It made it difficult for us to really control the game, it was a game that was up and down which is not really what we like."
Van 't Schip admitted the loss was disappointing given they slipped further behind the top six but insisted he was far more displeased with the insipid performance from his team.
"We're still there, we've made it difficult for ourselves. It was already a lot more difficult a few weeks ago, so that's why I said we should take it game by game," he said.
"This of course is a disappointment but more because of the way that we played not because of the loss.
"The loss of course, everyone wants to win, but I'm also looking at the way that we played and I think we can do a lot better."
Heart were slightly the better team in the first half but were punished for their inability to convert chances as an in-form Taggart stepped up to give the hosts a vital three points.
The patchy Hunter Stadium turf made it difficult for both sides to gain any fluency in their passing and subsequently the match turned into a scrappy affair punctuated by a succession of fouls.
"There was nothing really going on, we were not playing good ourselves, they were not having a good game. For the neutral watcher it wasn't a good game," van 't Schip said.
"It could have gone both ways I think this game and this time it went the way of Newcastle."
