Tonga coach Toutai Kefu named Siate Tokolahi and Patrick Pellegrini as replacements. Tokolahi will be one of six props in the Tongan squad. Pellegrini will back up first-choice No. 10 William Havili, whose older brother David is in the New Zealand squad.
Neither Fotuaika nor Mausia played in Tonga's 59-16 loss to Ireland on the weekend.
Tonga faces Scotland next in Nice and also will play defending champion South Africa and Romania in Pool B.