Zambia's preparations for the upcoming Africa Cup of Nations tournament suffered a blow on Thursday as veteran defender Stoppila Sunzu was forced to cut short his training session at Heroes Stadium due to an apparent knock. Sunzu, the hero who scored the winning penalty in Zambia's 2012 AFCON triumph, is one of 30 players currently in camp with the Chipolopolo Boys as they gear up for the continental showpiece in Ivory Coast next month. The team is set to depart for Saudi Arabia soon for a final training camp and two friendly matches before heading to their group stage destination. However, Sunzu's participation in the tournament now hangs in the balance after he picked up the knock during Thursday's session. The extent of the injury is yet to be determined, with doctors still assessing his condition and an official statement expected soon. The 34-year-old's returned to the national team setup in June after a three-and-a-half-year absence had been a major boost for Zambia. His first game back, a 3-0 home victory against Ivory Coast, secured the Chipolopolo Boys' place at the AFCON finals. Since then, Sunzu has re-established himself as a key cog in Avram Grant's defense, his experience and leadership qualities proving invaluable. His potential absence would be a significant blow to Zambia's hopes of success in Ivory Coast. The Chipolopolo Boys have been drawn in Group F alongside Morocco, neighboring Tanzania, and the Democratic Republic of Congo. Sunzu and Evans Kangwa are the only two players remaining from the 2012 AFCON-winning squad, and their presence in the team serves as a source of motivation for a younger generation who have missed out on the past three editions of the tournament. Zambia will be pushing for their second continental crown, but the uncertainty surrounding Sunzu's fitness adds an unwanted layer of tension to their preparations.