His father was in the French navy, and Nancy therefore spent his early childhood frequently moving, with time in Guadeloupe, Martinique, Djibouti and Réunion.

He also had stints at various amateur and semi-professional clubs, including Beaucairois, Raon-l'Étape, Ivry, Noisy-le-Sec, Châtellerault, and Orléans before moving to Canada in August 2005 to play with the UQAM team.

[9][10] On 28 May 2021, after just seven games as head coach, it was announced that CF Montréal had exercised its option on Nancy's contract for the 2022 season.

[11][12] Nancy lead CF Montréal to the final of the 2021 Canadian Championship, beating Toronto FC 1–0, qualifying them for the 2022 CONCACAF Champions League.

[18] Nancy narrowly lost the MLS Coach of the Year award, losing by one-tenth of a percentage point to Jim Curtin.