Argentina lost their unbeaten record in 2010 World Cup qualifiers on Tuesday as Colombia took advantage of a first-half red card for Argentina's Carlos Tevez to win their match 2-1, while Venezuela hit back three times to beat Bolivia 5-3.
Dayro Moreno scored an 83rd-minute winner for Colombia in Bogota after Manchester United forward Tevez was dismissed in the 25th minute for a petulant kick at Ruben Dario Bustos. Messi scored first for Argentina while Bustos netted the equaliser.
Venezuela, after clawing their way back three times to level with Bolivia, then scored twice in the last two minutes following an injury to visiting goalkeeper Carlos Arias.
The results opened up the single South American group, a marathon two-year contest in which each team plays 18 games.
Argentina stayed top with nine points from four games, while Colombia went second with eight and Venezuela moved on to six. Bolivia, already struggling, have only one point. Brazil have a game on hand against Uruguay.