Senna, a key member of Spain's UEFA EURO 2008-winning side, has recovered from the hamstring injury that forced him to miss this summer's FIFA Confederations Cup tournament and the recent friendly with FYR Macedonia and takes his place in a 22-man party.
The 33-year-old midfielder is the only addition to the squad selected for the Macedonia match, with Osasuna defender Ignacio Monreal, who was called up for the first time to cover for the injured Sergio Ramos, retaining his place. Spain play hosts to Belgium on 5 September in La Coruna before meeting Estonia in Merida four days later.
Vicente del Bosque's side have a 100 per cent record after six qualifying games, leaving them top of Group 5, six points ahead of second-placed Bosnia-Herzegovina and within touching distance of a place in next year's finals in South Africa.
Squad: Iker Casillas (Real Madrid), Jose Reina (Liverpool), Diego Lopez (Villarreal); Raul Albiol (Real Madrid), Alvaro Arbeloa (Real Madrid), Joan Capdevila (Villarreal), Carlos Marchena (Valencia), Ignacio Monreal (Osasuna), Gerard Pique, Carles Puyol (both Barcelona); Xabi Alonso (Real Madrid), Sergio Busquets (Barcelona), Santi Cazorla (Villarreal), Cesc Fabregas (Arsenal), Xavi (Barcelona), David Silva, Juan Mata (both Valencia), Albert Riera (Liverpool), Marcos Senna (Villarreal); Daniel Guiza (Fenerbahce), Fernando Torres (Liverpool), David Villa (Valencia)