JOHANNESBURG, Jan 6 (Reuters) - Africa"s showpiece Cup of Nations kicks off in Cameroon on Sunday against a backdrop of controversy over player call-ups, the tournament’s timing, the host nation’s readiness and the possibility of widespread COVID-19 infections. Yet what is not clear is who is likely to be crowned continental champions after the final on Feb. 6, as a multitude of prospective winners make it likely that the tournament will maintain its tradition for rarely delivering on the form book. Algeria are defending their title and go into the tournament with a lengthy unbeaten run, including their triumph at the last edition in Egypt in 2019. Led by Manchester City"s Riyad Mahrez, they have been rarely stretched over the last 24 months but the rigours of tournament competition, plus the tough conditions in Cameroon, will provide a severe examination. Egypt, Morocco and Tunisia are the other North African countries who are perennial contenders but have disappointed in recent editions. Morocco, in particular, have gone into recent tournaments heavily fancied but have proved unable to live up to their billing. West African giants Ghana, Ivory Coast and Nigeria are all past winners with high hopes, but have not been convincing of late. Nigeria fired their coach Gernot Rohr last month, unhappy with their form despite the fact they won their World Cup qualifying group. Hosts Cameroon have been even less convincing, but their home win over the Ivorians in the World Cup qualifiers in November was a massive morale boost and has now placed a burden of expectation on their shoulders. That leaves Senegal as the team with the best credentials. They were runners-up in 2019 and have strengthened their squad since, persuading several French-born players with Senegalese roots to join their side. Liverpool"s Sadio Mane could play a key role in helping the country to their first Cup of Nations triumph. All contenders will be hoping to avoid any outbreaks of COVID-19, which might impact on their chances. Preparations for most countries, over the last fortnight, have been hit by players returning positive tests and having to go into quarantine. Senegal’s departure to the tournament on Wednesday was delayed by three positive cases and the Cape Verde Islands have had an astonishing 21 individual positive cases at their pre-tournament training camp. RACE TO BE READY Squad sizes for this tournament have been increased from 23 to 28 to allow for the potential impact of the novel coronavirus. Teams will also have to contend with inferior hotel and training facilities, with Cameroon, stretched by poor infrastructure, racing to get ready before Sunday’s kickoff. The tardy preparations prompted an emergency meeting last month of the Confederation of African Football’s executive committee, which considered cancelling the tournament. After an emergency trip to seek assurances from the Cameroon government, CAF president Patrice Motsepe has gambled on going ahead, hoping to avoid any major calamities and that the football will claim the spotlight when the action begins.