United were beaten 2-1 at Ashton Gate after Korey Smith scored in the third minute of stoppage time to set up a semifinal tie with Manchester City.

Mourinho took the chance to rest a number of regulars but still picked a team which included Paul Pogba, Marcus Rashford, Anthony Martial and Zlatan Ibrahimovic. And after watching his team surrender the trophy they won last season, Mourinho accused some of his stars of failing to turn up.

"In the first half we lacked the intensity that they had," he told Sky Sports. "When I say intensity, I don't just mean physical, I also mean mentally. For some of us it was just one more day in the office. Probably a day that some of them don't even want to come to the office.

"For the Bristol boys, it was a big, big day and in the first half we could see that."

Mourinho then added on the club's official website: "The reality is that the ones [players] that were on the pitch were the ones that were not in the last match [against West Bromwich Albion] and are the ones that not going to be in the next match. I think they lost a good opportunity also to play semifinals and also to have two more matches to play.

"But I don't want to blame the players at all because I think they were professional -- it wasn't a case of 'we don't care about the game' or 'we don't have responsibility' or 'we don't have pride'. I think they showed they had that after the 1-0 and they had that until they scored the second goal in the last few seconds and we had no chance to react."

Mourinho insisted afterwards that Lee Johnson's side had been "lucky" but only because Smith's goal left United with no time to respond.

United hit the woodwork twice before Joe Bryan's fantastic strike gave Bristol City the lead in the second-half. Zlatan Ibrahimovic equalised from a free-kick, his first goal since returning from a knee injury.

Mourinho added: "My thoughts are that they were a bit lucky but they fought a lot to be lucky. They win the game in a moment where we have no possibilities to react. They win the game in our best moment in the game.

"They win the game in the moment where everyone was waiting for our goal. So I have to say they were a bit lucky. Also in the first half we hit the post twice before the score the first goal. But they played brilliantly, they fought like this was the game of their lives, which it probably was and it's nice to be like that.

"And a beautiful day for football because a team from a lower division won and get into the semifinals. A big day for them, a big day for their supporters so I want to congratulate them and I don't want the fact that I say they were a bit lucky to be the main thing. The main thing is that they won and fought hard for it.

"The most important thing was that a Championship team beat a club like Manchester United. In this club, we know how to win, we know how to lose, so we lost saying congratulations to them and good luck for the semifinal."

Bristol City's reward is a two-legged semifinal with Pep Guardiola's Premier League leaders, while Chelsea will play Arsenal.