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River Plate stunned Tigre with a stoppage-time goal to win their opening match in the new Argentine Apertura championship with a one-nil win on home soil.
The visitors went closest to scoring in a keenly-contested first half: Tigre Martin Galmarini arrowed a shot towards goal on 24 minutes - but the ball rattled back off the post. Another chance followed immediately.
However, this time Denis Stracqualursi headed into River Plate goalkeeper Juan Carrizo's arms.
The home side had little to show for their first-half endeavours, although captain Ariel Ortega briefly raised expectation levels with this effort seconds before the interval.
In the second half and with only seconds gone, Tigre midfielder Diego Castano let fly from distance. It forced Carrizo to make a smart save.
River went on to win the match in the first minute of stoppage time. The dramatic goal came from 19-year-old striker Rogelio Funes Mori. Mori was left with a simple header thanks to Ortega's cross after a hefty punt up field. River are away next Sunday at Huracan, a day after Tigre host Arsenal de Sarandi.