Michael Carrick has admitted that things "just didn't work" when David Moyes was manager of Manchester United.
Moyes succeeded Alex Ferguson after he stepped down at the end of the 2012-13 season, in which United won their 20th top-flight title.
However, the former Everton boss endured a dismal campaign at Old Trafford and was sacked following a 2-0 defeat against his old club in April 2014 - a result that ensured United would not qualify for the Champions League.
Carrick has denied that there was unrest in the dressing room during Moyes' tenure but has conceded that the season was a difficult one.
"It was a tough time. I think we can all say that with Sir Alex leaving and the changes that happened after that. It was a tough season, there's no getting away from that," he told Sky Sports News.
"We had some success in the Champions League and we weren't too far away from getting past Bayern [Munich] in the quarter-finals so it's fine margins I think. When you look at it, it just didn't work that season and we didn't have a great season in the end.
"Unfortunately for David, he lost his job so I'm sad how it finished but I suppose that's football. If you don't get the results, and you're the manager, you suffer for it.
"Of course it was going to be a tough job to take, but whether it was impossible or not, I'm not sure. I wasn't sitting in that seat and I wasn't in the position to be manager. You'd have to ask him I suppose.
"Just because it's tough times, it doesn't mean there's fighting and you don't get on or not like each other. Sometimes things just don't work out for many different reasons and that was the case."
United face Moyes' Sunderland on Sunday looking to bounce back from back-to-back draws against West Brom and Everton, which have put a major dent in their hopes of a top-four finish.