Defender James Jennings has transferred to Mansfield Town for an undisclosed fee.
Jennings, 25, joined the U's from Kettering Town in 2010 and has started exactly 100 league games.
He was appointed vice-captain after a year with the club, and has worn the captain's armband on a number of occasions at the R Costings Abbey Stadium.
Director of Football Jez George explained the surprising move: "We've been sympathetic to the fact that, for personal reasons, James has wanted to move to a club nearer his home in Manchester, so we allowed this deal to happen."
"The timing isn't ideal but like everything else we've had to deal with in the last three months we will get on with it and move on. We wish James all the best in the future and thank him for his time at Cambridge United."
Jennings was quick to point out that this was an honestly-motivated move: "The reason for me moving is purely for personal reasons, not for any football reasons."
"These things happen sometimes and I’ll be sad to leave the club. I've got great memories from being here and developed excellent relationships with some good people." he said.
Jennings continued: "I'd also like to thank people behind the scenes who have supported me since I've been here – Eddie (Clark, vice-chairman) and his family, Renford (Sargent, director) and Dave (Doggett, chairman).
"I’d particularly like to thank the fans for their support over the last couple of years and wish them well. I'd also like to thank my team mates and the staff, and send my best wishes to Jez and Richard for the rest of the season.
"I hope the club gets back to where it deserves to be and look forward to coming back here in the future, both to play and watch a few games."