The Bordeaux player was however confirmed ‘okay’ after he received treatment at a nearby hospital where he was rushed to.
Kalu was reported to have fallen while trying to take a corner-kick in Friday’s training session in Alexandria, and was immediately rushed to the hospital.
The 21-year-old underwent several medical examinations upon arrival in the hospital and he was rather confirmed to have collapsed due to dehydration.
Nigeria Football Federation (NFF) media chief Demola Olajire confirmed the situation, with a relief message that the Bordeaux winger has been advised to drink more water.
“I have been told Samuel Kalu has been stabilised. He was taken to hospital for tests and he is certified okay. He was dehydrated, they said. Told him he needs to be taking enough fluids,” Olaajire said.
Kalu is one of the nine forwards in Nigeria coach Gernot Rohr’s squad and it remains to be seen if he would be available for their Group B opening game against the Swallows at the Alexandria Stadium.
During the 2018-19 season, the pacy winger contributed three goals and two assists in his debut season with Bordeaux in the French Ligue 1.
Earlier this year, Kalu’s mother was kidnapped by gunmen as she travelled home in Abia.
Ozuruonye Juliet was released six days later although it remains unclear if a reported ransom was paid.