Promotion-seeking Whites were dealt with two huge defeats last week at a crucial stage in the Championship.
Ezgjan Alioski suffered a torn Meniscus in the game against Brentford and will be out for the rest of the season.
Barry Douglas, Bielsa’ s preferred left-back, will also be absent for the season, owing to an injury picked up months ago.
And the Argentine manager has given the nod to Dallas for Sunday’s crunch clash.
With options like Leif Davis and Liam Cooper on the table, the former Chile manager has chosen the Northern Irish man.
Dallas, 28, has represented the Whites for more than 120 matches.
He has the ability to play on both the wings and is normally deployed as a left-back.
However, Bielsa has used Dallas as a right-back throughout this season.
Dallas has made 24 appearances so far this season and his progress got impeded by a foot injury.
Leeds’ automatic promotion hopes are all but over now, as their promotion rivals Sheffield United are 6 points ahead of them with a superior goal difference.
LUFC will not end up in the Playoffs even if they win their remaining games unless Sheffield United suffer a heavy defeat in their final game, which is highly unlikely.
They will be up against a Villa side, who have been on a terrific run in recent times. Dean Smith’s men are fifth in the table and are unbeaten in their last ten games.