Ligue 1 - Nice snap up Digard
Digard, 25, spent last season on loan with the Ligue 1 outfit and has now secured a full-time contract at Stade Municipal du Ray, signing a three-year deal after the two clubs agreed an undisclosed fee.
Nice coach Eric Roy said: "Didier will play in front of the defence.
"This is a pivotal position in modern football and he has all the qualities to do so."
Digard joined Middlesbrough in a £4 million, four-year deal from Paris St Germain in 2008 but struggled to hold down a first-team berth at the Riverside.