The Red Devils drew 1-1 with Chelsea on Thursday night, with Cristiano Ronaldo cancelling out a Marcos Alonso opener.
There were no substitutions from Rangnick until 79 minutes of the contest when he brought on Mata and Phil Jones, which Keane cannot get his head round.
Mata is leaving this summer, while Jones does not appear to have much of a future at the club and Nemanja Matic is also departing and the Serbian started the match.
Keane would like to see young players given a chance and United building for the future, with the likes of Hannibal Mejbri, Alvaro Fernandez and Shola Shortire all unused substitutes, while Alejandro Garnacho only came on during stoppage time.
‘Tonight we are talking about Matic getting interviewed after the game that he’s leaving there’s three games to go. Stop talking!’ Keane said on Sky Sports.
‘Mata’s come on tonight again, he’s come on the last few games. You’ve got some young players on the bench, get them on. It’s like a tribute to Mata, I thought it was his testimonial tonight.
‘You’re Man United, you’re fighting for points, you’re playing for pride. But it’s all like, “We’ll give him a game, we’ll bring [Phil] Jones on, everyone gets a round of applause.”
‘You’re there to try and win a game for Manchester United forget all this give someone a game because he’s leaving in a few weeks. Actually you should have left two years ago yet they are all coming on and getting 20 minutes.
‘Get some of the young lads on. They’re hopefully going to be there for the future so give them a taste of Old Trafford and playing against really good players.
‘Mata is leaving in a couple of weeks, you brought him on last week. Mata’s not going to come on and change the game. He should have left last year and they gave him another year, I don’t know why. Jobs for the boys. He’s pals with this or that chief executive. Who is giving out these contracts? Crazy.’
Also expected to leave Old Trafford at the end of their contracts this summer are Paul Pogba, Jesse Lingard and Edinson Cavani.
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