Mexico's Cruz Azul drew 1-1 with Libertad of Paraguay in the first leg of its Copa Libertadores Round of 16 tie.
The match started badly for Cruz Azul, as Libertad's Pablo Velazquez unintentionally knocked out Jose de Jesus Corona with his left knee as the goalkeeper raced off his line to deny the attacker an opening.
Yosgart Gutierrez came on to replace Corona in the 14th minute and the Mexican team went ahead through Javier Orozco's goal in the 27th minute.
However, Velazquez headed a free-kick into the back of the net to level in the 70th minute to give his side the edge ahead of the second leg.
Atletico, which changed coach at the weekend, replacing
Velez could have widened the gap in the 54th minute with a penalty, but
It was the first victory on Colombian soil for Velez in continental championships.
"The worst thing we can do is to think the tie is finished," coach Gareca told reporters.
"In Buenos Aires, we'll have to make a big effort. We have claimed a very important win but it is not decisive."