Mechele was a surprise choice in the squad Martinez named on Friday when he also recalled Jason Denayer, Christian Kabasele and Dennis Praet.
There are a host of Premier League players in the squad, with Chelsea's Eden Hazard, Manchester United's Romelu Lukaku and Marouane Fellaini, Tottenham's Toby Alderweireld, Liverpool's Simon Mignolet, Manchester City's Vincent Kompany and Watford's Kabasele all being included.
Belgium, who are now top of the FIFA rankings despite finishing third at the World Cup in July, host Switzerland in Brussels on Friday, October 12 in the Nations League and then the Dutch in a friendly four days later.
Martinez's side commenced their Nations League campaign last month with a 3-0 victory away to Iceland.
Goalkeepers: Koen Casteels, Thibaut Courtois, Simon Mignolet, Matz Sels
Defenders: Toby Alderweireld, Dedryck Boyata, Jason Denayer, Christian Kabasele, Vincent Kompany, Brandon Mechele, Thomas Vermaelen
Midfielders: Yannick Carrasco, Timothy Castagne, Nacer Chadli, Marouane Fellaini, Thomas Meunier, Dennis Praet, Youri Tielemans, Hans Vanaken, Axel Witsel
Forwards: Michy Batshuayi, Eden Hazard, Thorgan Hazard, Romelu Lukaku, Dries Mertens, Leandro Trossard