Democratic Republic of Congo club TP Mazembe are on high alert before a CAF Champions League quarter-final in Tanzania Saturday after 'dirty tricks' allegations against opponents Simba SC.
Another Congolese side, V Club, said they were unable to use the changeroom in Dar es Salaam ahead of a group game last month because of a "strange smell".
Coach Florent Ibenge added in a radio interview that he believed the bottled water available to the teams during the match included a substance that induced drowsiness.
Roared on by a capacity 60,000 crowd, Simba came from behind to defeat V Club 2-1 through a last-minute Clatous Chama goal and secure a place in the knockout stages.
Mazembe said in a statement that other clubs who played Simba in Tanzania this season had complained of being given "a poor quality bus in which there was an unpleasant smell".
The five-time African champions said the match organisers must ensure there is "no attempt to influence the result in violation of the rules and regulations".
Neither African football body CAF nor Simba have commented on the allegations made by various clubs who met Simba.
AFP Sport previews the first legs with five former champions, Mazembe, Al Ahly of Egypt, Esperance of Tunisia, Mamelodi Sundowns of South Africa and Wydad Casablanca of Morocco, involved.
Simba v Mazembe
Simba are formidable at home, winning all five qualifying and group games with record eight-time champions Ahly among the victims.
They have scored 13 goals in those matches thanks to a strike force comprising Tanzanian John Bocco, Zambian Chama, Rwandan Meddie Kagere and Ugandan Emmanuel Okwi.
Vastly experienced Mazembe, the second most successful club in CAF competitions with 11 titles, have drawn three of four away matches and are expected to win the tie.
Sundowns v Ahly
"We are small boys compared to Ahly," says Sundowns coach Pitso Mosimane as the Pretoria outfit seek a first victory over the Cairo Red Devils after four failed attempts.
The tie is a repeat of the 2001 final in which Sundowns were held 1-1 at home and fell 3-0 away. Ahly won 2-0 at home and drew 2-2 away six years later in a qualifier.
Themba Zwane has scored five Champions League goals this season and will need to be on form again as Sundowns must win at home to have a realistic chance of making the semi-finals.
Horoya v Wydad
Guineans Horoya have reached the last eight for the second successive season and hope for a better showing this time after a four-goal hiding from Ahly last year.
They have gambled by firing coach Patrice Neveu after qualifying from a difficult group and replacing him with another Frenchman, Didier Gomes da Rosa.
Da Rosa must pit his wits against Wydad handler Faouzi Benzarti, a veteran Tunisian and the most successful African coach in CAF club competitions with five titles.
Constantine v Esperance
Defending champions Esperance made impressive progress to the last eight by winning four matches, drawing two and conceding only two goals.
Coach Moine Chaabani is relying heavily on the team that defeated Ahly 4-3 in the two-leg 2018 final, which includes Tunisian, Algerian, Cameroonian, Ivorian and Libyan stars.
Constantine have reached the quarter-finals for the first time and the highlight so far of the campaign was thrashing Mazembe 3-0 at home in a group game.