Dos Santos had to come off before the second half of Tuesday's semifinal match after picking up an injury.
"Unfortunately, he has a muscle injury," said Luis Fernando Tena to the assembled media after the win. "[We] don't know the magnitude of the injury yet, we have to wait and run some tests."
Dos Santos surprisingly came off at the start of the second half, being replaced by Raul Jimenez, fueling speculation that something was wrong with the Tottenham player.
Pressed for a prognosis, Tena said that the extent of the injury has not been sufficiently identified.
"I don't know, he's doubtful at this point. We have to find out," the Mexico U-23 manager said.
Although not having Dos Santos for the Olympic final would certainly be a talking point, Tena instead focused on the rest of his team, highlighting the players' ability to overcome adversity thus far.
"The players have a new mentality, they want to play abroad now, they have no complexes and they want to succeed."
Finally, Tena revealed that Mexico's unprecedented run has already yielded a call from the country's president, Felipe Calderon.
"I'm happy that we've been able to provoke such euphoria in such a soccer-mad country as ours," finished Tena.
Additional reporting from London was provided by Mike Slane.
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