Buenos Aires - Brad Weber gate-crashed the Jaguares' party in Argentina Saturday to snatch a 30-26 Super Rugby victory for the Chiefs from New Zealand.
The scrumhalf, who came off the bench to replace All Black Tawera Kerr-Barlow in the second half, scored the match-winning try two minutes from time in Buenos Aires.
Leading Super Rugby points scorer Damian McKenzie converted from the touchline, leaving the Buenos Aires-based hosts needing a try to regain the lead.
But the South Americans lost possession from the kick-off and the relieved Chiefs booted the ball into touch for a third victory in four outings this season.
Playing at home for the first time after a win and a loss in South Africa, debutants Jaguares looked set for a dramatic win when they scored two tries in as many minutes to turn a nine-point deficit into a 26-23 advantage.
A Santiago Cordero break led to a five-metre scrum, and after two resets scrumhalf Martin Landajo dotted down with flyhalf Nicolas Sanchez converting on 72 minutes.
Within a minute the sell-out 25,000 crowd at Estadio Jose Amalfitani were back on their feet as a dazzling 90-metre handling move ended with substitute Matias Moroni diving over far out.
Leading 2015 Rugby World Cup points scorer Sanchez failed to convert, but Jaguares had a three-point advantage with six minutes left.
Chiefs stormed back, moved into Argentine territory and kept the ball alive long enough for Weber to dive over and stun the crowd.
It was a thrilling climax to a pulsating seven-try encounter full of running rugby which saw the Argentines take a 14-13 lead into half-time.
The Jaguares will regret not taking more advantage of a 10-minute numerical superiority either side of the break when Kerr-Barlow was sin-binned for a professional foul in the 39th minute.
Both sides kicked one penalty while the New Zealanders were a man short and when Kerr-Barlow was eligible to return, Weber came on.
Wingers Sam McNicol and James Lowe, fullback Damian McKenzie and Weber were the try-scorers for the Chiefs, Super Rugby champions in 2012 and 2013.
McKenzie kicked two conversions and a penalty and flyhaf Aaron Cruden one penalty for a visiting team lacking several injured stars, notably All Blacks lock Brodie Retallick.
Hooker and skipper Agustin Creevy, Landajo and Moroni crossed the try-line for the Jaguares, whose starting line-up contained 14 Argentine Test players.
Sanchez stotted one conversion and three penalties from five shots at goal.
Jaguares have home advantage again next weekend, against the Western Stormers from South Africa, while the Chiefs host Western Force from Australia.