Giggs added that Bale is rated only “50/50” to make his Wales return in time to play against Republic of Ireland in Tuesday’s crucial Uefa Nations League clash in Dublin.
"Gareth has got a little bit of muscle fatigue and he won't be involved against Spain," Giggs said. "We don't want to take any risks and we are monitoring it every day. I would say he is 50-50 at the minute for the Ireland game."
Bale made an impressive start to the new season with five goals and three assists in his first seven appearances for Madrid, though he has failed to find the net in his last three La Liga games.
He also played a starring role for Wales in their comprehensive 4-1 victory over Republic of Ireland at the Cardiff City Stadium back in September, registering a goal and an assist.
Wales followed up that win by losing 2-0 against Denmark in Aarhus, leaving them second in Group 4 of the Uefa Nations League’s second tier after two matches.
A crowd of almost 50,000 tickets have been sold for the visit of Spain to the Principality Stadium, where the roof will be closed due to forecast rain.
Stoke City midfielder Joe Allen said of Bale: “He always can't wait to meet up with us and it's great to have your talisman here.
“Hopefully he's going to be all right and it goes without saying how important he is to us.”
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