Born in Salies-de-Béarn, Capdouze began his rugby union career with A.S. Salies before moving to U.S. Dax at age 17.

He later joined Section Paloise, where he played a decisive role in the club's victory in the 1963–64 French Rugby Union Championship, scoring all 14 points in the final.

Upon recovery, Capdouze briefly joined S.A. Saint-Sever, and winning the military championship with the Nansouty barracks in Bordeaux.

His talent attracted attention, with six clubs—including CA Bègles, Aviron Bayonnais, FC Auch, Stade Toulousain, and US Romans Péage—vying for his signature.

In the French Championship final, Capdouze scored 11 points in a 14–0 victory over Béziers, securing the third Bouclier de Brennus in the history of la Section.

[5][6] His performance earned him a spot in the France national rugby union team, coached by Jean Prat, for the 1964 tour of South Africa.

During this period, Capdouze transitioned to playing as a centre, with Pierre Albaladejo, at the peak of his career, retaining the fly-half berth.

However, after earning six caps, he made a surprising switch to rugby league following a disagreement with his Section Paloise captain, François Moncla.

[8] Capdouze was selected as the stand-off half for France in the 1968 Rugby League World Cup, co-hosted by Australia and New Zealand.