Defender Nicolas Otamendi sneaked a late equaliser as Argentina, without injured captain Lionel Messi, came back from two goals down for a 2-2 draw away to Venezuela on Tuesday.
The Venezuelans were deserving of their second point in eight qualifiers after goals by young forward Juanpi Anor and striker Josef Martinez had their opponents on the ropes.
But striker Lucas Pratto pulled one back with his maiden goal in his second match for Argentina, putting the visitors' tails up after a sluggish first hour in the wet in Merida.
Uruguay had no such problems with equally damp conditions at home in Montevideo where they crushed Paraguay 4-0 with a Luis Suarez masterclass and an Edinson Cavani brace.
Suarez laid on both goals for Cavani and also converted a penalty on the stroke of halftime after midfielder Cristian Rodriguez had scored Uruguay's second.
Cavani went top of the group's scorers with five goals in eight matches.
Uruguay snatched the lead in the South American group back from Argentina, who went top on Thursday after beating them 1-0 at home thanks to a Messi goal.
Uruguay have 16 points to Argentina's 15 after eight rounds in the 10-nation South American group with two others to be completed later on Tuesday.
South American champions Chile were held 0-0 at home by improving Bolivia and remain in the bottom four while Venezuela prop up the table with two points.
The top four go through to Russia while the fifth-placed team qualify for an intercontinental playoff.
Argentina were stunned when 22-year-old Juanpi skipped between two defenders on the right of the box and curled a superb left-foot shot into the top far corner in the 34th minute.
The best Argentina could muster in the first half was a shot from outside the box that skimmed the post by Ever Banega, who was wearing Messi’s number 10 shirt.
Martinez doubled Venezuela’s lead seven minutes after the break when he scored from a low cross by the ever busy and dangerous Salomon Rondon, who skipped past Otamendi.
Pratto struck six minutes later and Argentina piled on the pressure in the final stages with Venezuela’s goalkeeper Daniel Hernandez forced into a fine save to deny Angel Di Maria and keep his side ahead.
However, Otamendi made amends in the 83rd minute for his poor performance at the back by steering in a corner from the right at the near post to save Argentina's blushes.
(Reporting by Rex Gowar; Editing by Ian Ransom)