Six players suffered burns on the soles of their feet after playing on an artificial pitch in blazing sun, Peruvian club Sporting Cristal said on Wednesday.
Cristal said Juan Cominges, Jose Mendoza, Miguel Villalta, Carlos Lobaton, Erick Delgado and Gabriel Garcia had been unable to train properly this week because of burns and blisters on the soles of their feet.
Uruguayan striker Garcia was the worst affected. "You can't imagine how much it burns," he told the newspaper El Comercio.
The team kicked off the season away to Alianza Atletico at the Miguel Grau stadium last Saturday in searing summer heat.
"Artificial pitches are completely wrong when you have to play in that kind of heat," Sporting Cristal director Jose Osterling told the Andina news agency.
Osterling said he had asked the Peruvian league for all matches on artificial pitches to be played at night.
Several Peruvian grounds, including the National Stadium in Lima, installed artificial pitches for the World Under-17 championship which the country hosted in 2005.
The pitches have been widely criticized by coaches.
"Can you imagine Brazil and Argentina coming here to play and not complaining," said Alianza Lima coach Gerardo Pelusso.
Costa Rica played its home matches in the 2006 World Cup qualifying competition on an artificial pitch at the Saprissa stadium.