Saudi Arabia stunned Lionel Messi's Argentina 2-1 with brilliant individual goals from Saleh Al-Shehri and Salem Al-Dawsari during the FIFA World Cup Group C match on Tuesday.
Messi said his team knew Saudi Arabia, despite being the team ranked second-lowest in the tournament, could hurt them.
Mexico's exit ended a run of seven successive last-16 appearances at the World Cup and the defeat for Saudi Arabia killed off what had looked to be a realistic chance of advancing from the group stages for the first time in 28 years.
Last week's surprise 2-1 win over Argentina means victory over Mexico on Wednesday would take Saudi Arabia into the next round in Qatar and the Green Falcons' improved performances have come as a result of increased professionalism domestically.
IMAGES from the FIFA World Cup Group C match played between Poland and Saudi Arabia at Education City Stadium on Saturday.
Saudi Arabia, FIFA's 51st ranked team and who have suffered 5-0 and 8-0 World Cup defeats down the years, roared back to claim an astonishing 2-1 victory that will go down as one of the greatest shocks in any sport ever.
Saudi Arabia's 2-1 victory over Argentina is rated the biggest shock in World Cup history.
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