McGuane has joined United’s Sky Bet Championship rivals Bristol City, where he will link up with former U’s head coach Liam Manning.

The midfielder didn’t feature in any of United’s matchday squads this season, being left out for Championship games against Norwich City and Coventry City, plus the Carabao Cup victory over Peterborough United.

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Last season, McGuane was dropped by Buckingham in the aftermath of the 5-0 defeat at Bolton Wanderers in March, and was left out of the next four matchday squads, before returning to the fold as a substitute in the 5-0 win against Peterborough.

U’s head coach Buckingham said: “Marcus has been a wonderful servant for this football club, and a player more to the point.

“He’s helped us get where we are now. He had a wonderful start to the season, and when I came in, he carried that form on, and then fell out the team.

“The way he applied himself from that moment was a large reason as to how he got back in the team and performed, and was trusted.

“Certainly in the play-off games when we made the change away at Peterborough, and when we had to make that change after 60 minutes at Wembley.

“He’s a very good player, and with the signings that we’ve made, we’ve signed a lot of midfield players, it’s not right to hold Marcus here.

“We could do, but it would prevent him playing. He’s got an opportunity to go and do that at Bristol City, and we wish him well, and thank him for his time here.”