Saul picked up the injury in the first leg of the UEFA Champions League last 16 tie with Bayer Leverkusen last month.
But Saul - who has three goals to his name this season - could be in line to make his comeback against Cordoba on Saturday.
A statement on Atletico's website read: "Saul Niguez was given the green light to rejoin team work with a medical discharge.
"The medical report confirms that the young red and white footballer "has received a medical and sports discharge after the left renal trauma with peri-renal haematoma" suffered in that match, [versus Leverkusen].
"And this afternoon, at 17:00 [local time], at Majadahonda's Sports City, Diego Pablo Simeone will have the player at his disposal in the first training session of the week to prepare for the next league commitment with Cordoba."
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