Ghana striker Majeed Waris faces a race against time to be fit for the World Cup in Brazil after scans revealed he has a torn quadricep.
The 22-year-old suffered the injury in only the fourth minute of Monday's 4-0 friendly win over South Korea.
The Black Stars' team doctor Adam Baba revealed Waris is improving and "can now bend his knee with little pain".
Should Ghana wish to call up a replacement they must do so by 15 June - 24 hours before their first match.
Ghana kick off their campaign against United states in Natal on 16 June.
They will also face Germany and Portugal in Group G.