Bale could make his debut tomorrow against Villarreal.
He said: "If he starts Saturday, he will not finish the game. I would be amazed if he does.
"We have looked at him in these 10 days and he is nowhere near ready for 90 minutes even if Spanish football is slower.
"He may start, but he won't finish the game.
"He may get 45 minutes, I don't know, but he will feel better in himself after 30 minutes here.
"But he has only had four training sessions in two months which is dangerous."
He added: "He played 30 minutes but after 15 minutes he looked tired - but he has only had four training sessions, so you will not get what you normally get.
"But he gave us a lift, the fans were excited and it gave us a spur, although the game was done and dusted.
"We needed to be in the game when he came on. It was lost by then, but it was nice for the Welsh supporters to see him."
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