Oxford United and Mansfield Town have reached agreement for centre back Rhys Day to join the Blue Square Bet Premier side on a free transfer.

The 28-year-old defender had been loaned out by Oxford to the Stags, and has been lining up at Field Mill alongside fellow former United players Kevin Sandwith, Adam Murray and Rob Duffy.

The permanent transfer may free up some money to help U’s boss Chris Wilder in his squad-building plans during the January window.

Signed from Aldershot in July 2009, Welshman Day, a former Manchester City trainee, turned out 19 times for Oxford United.

And he played his part in helping the team win promotion back to the Football League last season.

His last appearance came in the Conference Play-Off final against York City at Wembley on May 16, when he came on for the last few minutes.

Day’s games this season at Mansfield have not been without incident.

He was sent off in his second appearance, a 4-1 defeat at home to title-chasing Crawley Town.

Then, in successive matches over the Christmas period, he helped Mansfield triumph 5-1 at Cambridge on December 28, only for the team to go down 7-2 at Grimsby four days later.

Darlington were among the clubs reported to be interested in signing Day.

However, Mansfield’s new boss Duncan Russell concluded the deal, and he also completed the permanent transfer of former Oxford United skipper Murray from Luton Town.