The Blues recorded a 2-0 win to move two points clear at the top of the Barclays Premier League with Oscar and Diego Costa striking either side of half-time.
But Newcastle were dominant for much of the first 45 minutes before Oscar's opener and created the better chances - with Moussa Sissoko coming closest as he crashed an effort off the frame of the goal.
Chelsea were sluggish and wasteful in possession, with Mourinho jumping out of his dugout on more than one occasion to bellow out his feelings of discontent.
But Holland, again filling in for Mourinho for the club's media duties with the Portuguese set to sit out press conferences until his Football Association hearing for a misconduct charge is heard, praised the response of the players after the interval.
"We didn't have enough players playing quite at the level we are used to seeing in the first half," he conceded.
"The manager reminded one or two of them at half-time what was required and there was a good response from the players.
"It is very difficult to hit the level that people expect week in week out, particularly in this country. The players have had a real battering over Christmas so to reach that level that everyone wants to see week in, week out is impossible.
Chelsea could have had a penalty in the second half after a Costa cross struck the arm of Newcastle skipper Fabricio Coloccini but Holland refused to get drawn into another debate over referees - the very topic which has landed his boss in hot water.
"It could have been (a penalty) but it would be nice today not to talk about referees, I think the referee had a good game today and the team won today regardless," he said.
"Coloccini did have his arm in the air, the ball clearly struck his arm and had it not done it would have gone into the penalty area - but I think our preference would be to focus on the improved performance in the second-half."