Celtic tried to sign Michael Duberry last season, it has been revealed.
The 35-year-old former Chelsea centre-back has quit St Johnstone to sign a two-year deal with Oxford United.
And the League Two club's gaffer Chris Wilder has snapped up Duberry thanks to a recommendation by Parkhead coach Garry Parker.
Wilder said: "We don't just sign players on a whim. We've done extensive homework on Michael. He's mobile and he's ambitious.
"I've got to say a thank you to Garry Parker, who gave him a really good reference.
"Celtic showed an interest in him at Christmas and they were looking to bring him into the club, but Michael wanted to play regularly.
"He got his career back on track by playing football and going up to Scotland. He's been excellent up there.