His first-half penalty, Juan Roman Riquelme's brace and a late goal from Diego Milito ensured victory in Maracaibo for the Argentinians, although Liverpool midfielder Javier Mascherano was concerned by several defensive mistakes.
"We won an important match and played well," he said. "But we have to defend better after a corner-kick. We didn't expect their first goal.
"It is very difficult to maintain the pace as the temperature makes it very tough. It is hot and we are always trying to attack and have the ball."
Crespo is still 21 goals behind the record of 56 held by Gabriel Batistuta.
Paraguay, who beat the United States 3-1 earlier, top Group C by virtue of goal difference ahead of next Thursday's decisive match against Argentina.