Gerard Houllier has questioned the commitment of Stephen Warnock and Habib Beye and urged the full-backs to work harder.
Warnock, who went to the World Cup with England last summer, has fallen down the pecking order at Aston Villa since Houllier took charge.
He is currently the third-choice left-back behind Ciaran Clark and Nathan Baker and was linked with a loan move elsewhere in January.
Senegalese right-back Beye, meanwhile, has not been part of Houllier's plans for nearly three months.
Both players have now been relegated to training with the reserves and Houllier has demanded they show the right attitude before making a return to the first-team fold.
Give your best
He told the Birmingham Mail: "They must show the trust first and they must show they like the club.
"They're here, they're Aston Villa players, they are training with the reserves. If needed, they will fill in. If not, they won't.
"It's not only a matter of being good enough, it's also a matter of being committed enough.
"They're training with the reserves and they have to give their best because the reserves work hard.
"There's no point just being in our warm-downs, so they train with the reserves."