Rangers' Dujon Sterling and Ryan Naderi could feature in Sunday's Old Firm clash.
Both have trained, with Rangers boss Danny Rohl wanting to determine how both react physically to the session before selecting them.
Mr Rohl said: "Both are training; if it’s enough to be in the squad, I have to decide tomorrow.
"Today I can’t say if they’re in or out.
"I need to see their reaction to the session."
Sunday's game will be the first of two Old Firm fixtures within a week.
Ibrox hosts the league clash this Sunday, followed by the Scottish Cup quarter-final the following week.
The Rangers boss also expressed optimism about his players' readiness for the game against Martin O'Neill's side.
Rangers come into this match on the back of a disappointing 2-2 draw against Livingston last weekend, which sees them four points behind league leaders Hearts.
He said: "We feel ready. When you are a manager at home in these games you feel on fire.
"We have one more training, I feel the confidence and belief.
"We can speak about shape and tactics but it’s about how we go into the game, win duels, play forward."
Rangers currently sit two points ahead of Celtic, but the latter has a game in hand against Aberdeen.
