Ghana coach Milovan Rajevac has revealed that John Mensah is set to undergo medical tests on Monday.
The Sunderland centre-half has endured an injury-hit 2009/10 campaign, causing concern to both his club and international coaches.
His latest problem arose during the Black Cats' 1-1 draw with Everton on Boxing Day, with the African ace forced off with 19 minutes of the contest remaining.
A hamstring problem, which has been troubling him for a while, must now be assessed in an effort to determine the severity of the problem.
Rajevac, who is hoping to have Mensah available for the African Cup of Nations in the New Year, remains hopeful but admits the ongoing niggles are giving him an untimely headache.
"I am worried because Mensah is one of our most important players. He will have tests on Monday and then we will see," the Serbian coach told KickOffGhana.
"I spoke to him after the Everton game and he said he had to come off as a precaution. I hope it is nothing serious."