Mata had played in every game dating back to November but was in particularly poor form in the 1-0 win over Sheffield United, a game which effectively passed him by.
Speaking to BT Sport ahead of the game, van Gaal cited the fact Mata needed a rest as to why he didn’t start.
“Mata has played all the games, I think there was only one he didn’t play, so he needed a rest,” he said.
Louis van Gaal to BT Sport: "Mata has played all the games, I think there was only one he didn't play, so he needed a rest." #mufc
— Manchester United (@ManUtd) January 12, 2016
Regardless of whether Mata needed a rest, leaving him out against Newcastle was the right move because he really was poor at home in the Sheffield United game.
Towards the start of this season Mata was in fantastic form for an extended period of time for United but since the team has gone into a lull, Mata’s influence on games has dramatically dipped. He’s massively struggled on the right-wing in recent weeks but that’s not all to surprising given that it’s not his natural position.
Moving forward, Mata is still one of our most important players in the current squad but he definitely needs to improve his form and re-find the sort of performances he was putting in at the start of the season.