Belgium's all-time record goalscorer, on loan at Inter Milan from Chelsea, has not played since August due to a muscle problem.
Rennes winger Jeremy Doku is also out injured, with Martinez giving a first call-up to 18-year-old Anderlecht defender Zeno Debast.
Belgium will host Wales in Brussels on September 22 and take on the Netherlands in Amsterdam three days later in their final competitive game before the World Cup in Qatar.
The Belgians trail leaders the Netherlands by three points in Group A4 heading into their last two matches.
Belgium open their World Cup campaign against Canada in Al Rayyan on November 23, before further Group F games against Morocco and Croatia.
Belgium Nations League squad:
Goalkeepers: Thibaut Courtois (Real Madrid/ESP), Simon Mignolet (Club Brugge), Koen Casteels (Wolfsburg/GER), Matz Sels (Strasbourg/FRA)
Defenders: Toby Alderweireld (Antwerp), Jan Vertonghen (Anderlecht), Arthur Theate (Rennes/FRA), Thomas Meunier (Borussia Dortmund/GER), Timothy Castagne (Leicester City/ENG), Dedryck Boyata (Club Brugge), Zeno Debast (Anderlecht), Jason Denayer (free agent), Brandon Mechele (Club Brugge), Wout Faes (Leicester City/ENG)
Midfielders: Axel Witsel (Atletico Madrid/ESP), Youri Tielemans (Leicester City/ENG), Kevin De Bruyne (Manchester City/ENG), Amadou Onana (Everton/ENG), Hans Vanaken (Club Brugge), Alexis Saelemaekers (AC Milan/ITA), Thorgan Hazard (Borussia Dortmund/GER), Leander Dendoncker (Aston Villa/ENG)
Forwards: Michy Batshuayi (Fenerbahce/TUR), Lois Openda (Lens/FRA), Eden Hazard (Real Madrid/ESP), Leandro Trossard (Brighton/ENG), Yannick Carrasco (Atletico Madrid/ESP), Charles De Ketelaere (AC Milan/ITA), Dries Mertens (Galatasaray/TUR), Dodi Lukebakio (Hertha Berlin/GER)