Barcelona star Lionel Messi risks another spell on the sidelines if he plays the El Clasico against Real Madrid, Argentina's team doctor warned.

The Argentina international has been sidelined since sustaining a knee injury against Las Palmas on September 26.

There were hopes Messi would be fit for the November 21 clash against fierce rivals Real at Santiago Bernabeu.

But Argentina's team doctor, Homero de Agostino, said there was a chance Messi could face an even longer spell out if he played.

"The risk of aggravating the injury if Messi plays the El Clasico is high," he told Cadena SER.

De Agostino said he doubted whether the 28-year-old would be back to fitness in time for the top-of-the-table clash.

"I don't think that he can get in condition to play the Clasico," he said.

"The coach cannot rely on a newly recovered player."

Messi has been left out of the Argentina squad for upcoming World Cup qualifiers against Brazil and Colombia.