Whenever he was fit and played. Rafael is a red card waiting to happen but somehow had only 3 red cards, that's something superb for a player like him who is a fiery character.
He was at United seven years, and averaged 15 league games a season. That's how unreliable he is. There's no point keeping a backup player who can never play. Darmian in comparision was injured twice and somehow still managed to have 18 games this year. Once he adds a couple when his shoulder heals, he'll have more games than Rafael ever managed in one season, with exception of 2012-2013.
I said many times, he makes a cynical foul he is clueless and headless chicken, someone like Ivanovic makes a cynical foul, he is experienced and knows when to foul. These arguments are already done long back and how there are double standards when judging players.
They're not double standards because we're judging two different things. Rafael just loses his ****, fouls recklessly, refs see it and they book him. Ivanovic fouls cynically, with a cool head and he knows how not get booked. One is a good skill to have in a defender, the other is not. Carragher was a violent ****, for example, but he usually got away with it. Chellini fouls people in every contact, but he somehow always manages to play +40 games a season. And I could go on with examples.
Some players have a Master's degree in Dark Arts and they know how to get away with fouls. Some players are just not very bright. That's Rafael.