The defender has withdrawn from David Platt's squad with a nagging ankle problem that ruled him out of Saturday's 1-1 draw against West Ham.
Boss Glenn Hoddle revealed after that draw that Ledley had been included in David Platt's squad, rather than with Sven-Goran Eriksson's seniors, but he revealed: "Ledley has pulled out of the England Under-21s. He is injured."
But Matty will be able to build on recent impressive performances for the U21s - including last time out against Italy - as Platt's youngsters take on Portugal in a friendly at Stoke City's Britannia Stadium.
England U21s: Robinson, Kirkland, Bywater; Young, Wright, Barry, Riggott, Brown, Knight, Konchesky, Samuel; Pennant, Wright-Phillips, Davis, Carrick, Prutton, Jenas, Johnson, Dunn, Etherington; Defoe, Smith, Christie, Crouch, Zamora.
Ledley King will not be joining Matthew Etherington on England U21 duty on Tuesday.