The 31-year-old Milan midfielder came off the bench in the second half of the 2-1 loss in Natal as Ghana made a poor start to their Group G campaign.
However, he suffered a blow to his toe during the game and subsequently sat out the session on Wednesday.
The Ghana Football Association have not confirmed whether he is likely to miss their second group game with Germany but have revealed that the midfielder's condition is being watched closely by their medical team.
"Michael Essien sat out training on Wednesday as team medics monitor his fitness for Ghana's World Cup group clash against Germany on Saturday," read a statement on the Ghana Football Association official website.
"The Ghana midfielder picked up a toe injury during the Black Stars' defeat to the United States on Monday after coming on as a second-half substitute.
"Ghana's medical team are working to get him ready after watching training in Maceio from the sidelines."
Essien is appearing at his second World Cup but faces competition for a starting berth from Sulley Muntari and Mohammed Rabiu.
