The League Cup semifinal is on Sunday at Hampden.
Rangers are looking for a new manager before the League Cup semi-final.
The replacement may not be in the dugout for the game.
The club held positive talks with a former player at the weekend and have spoken to other candidates.
A working visa is required for a manager coming to the UK from abroad.
The new manager will need to assemble a backroom team, with the previous manager taking a number of staff with him to Villa.
Rangers announced on Tuesday that Jermain Defoe would be leading the team's preparations for the tournament.
The Glasgow side lead the Scottish Premiership by four points from city rivals Celtic and host Sparta Czech in a key European tie four days after the semi-finals.
