OXFORD United would have to receive a substantial bid to consider selling Cameron Brannagan, says Karl Robinson.

The highly-rated midfielder was the subject of an offer worth more than £500,000, thought to be from Millwall, late in the January transfer window.

United rejected the bid and Robinson confirmed the 24-year-old’s contract, which runs until summer 2023, leaves the club in a strong position.

The U’s head coach said: “There’s a buyout clause in Cameron’s contract in the summer that’s significantly higher than that.

“That was part of getting him to do a deal last summer.

“We’re very well-protected by the length of Cameron’s contract and the buyout clause.”

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Brannagan agreed a two-year contract extension last August, when there was less than 12 months left on his existing deal.

It followed an impressive campaign for United’s No 8, who made 39 appearances and scored seven goals to help his side reach the Sky Bet League One play-off final.

Brannagan played the first eight games of this season, before contracting rare inflammation behind the eye in mid-October that left him fearing he would go blind.

Doctors at the John Radcliffe Hospital saved his sight and the former Liverpool trainee was placed on a course of steroids, beginning a slow recovery process.

He returned at Burton Albion on January 2 and has featured in United’s last six matches, starting their two most recent League One games due to Marcus McGuane’s thigh injury.

The 22-year-old is expected to be back by the start of March, but his return could give Robinson a headache.

United doubled the number of loan players on their books with the deadline-day signings of Joe Grayson, Elliot Lee and Brandon Barker, who join McGuane, Mide Shodipo and Liam Kelly in the building.

Only five loanees are allowed in a matchday squad, but Robinson is confident it will not be an issue.

He said: “They all have to stay fit, first and foremost.

“Then it’s a case of whichever five suit that particular game.”