Ayala missed the midweek trip to MK Dons after falling awkwardly on his ankle during last weekend's clash with Blackburn Rovers - and Karanka says he will be assessing the player ahead of Monday's Elland Road clash.
"He is improving but we have to be careful because I don't want to take a risk like with Nugent against Reading or Stuani against Hull," said Karanka.
"I'll speak to him and if he isn't 100% he won't play because I will keep him for the next game."
Ben Gibson was partnered by Tomas Kalas at MK on Tuesday with returning defender Alex Baptiste still short of match fitness after being sidelined since July with a double fracture of the leg.
"Alex is training with the team and is showing that he is ready but still has to play in the Under-21s to get some games in," added Karanka.
"It would be difficult for him to come straight back into the Championship."
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