Saudi Arabia today defeated Argentina 2-1, causing one of the biggest upsets of World Cup history. Lionel Messi and his team lost in the first match of the group stage and were dealt a heavy blow

Lionel Messi said Argentina's shock loss to Saudi Arabia was a "very heavy blow" but vowed the South American champions would bounce back from the defeat.

"It's a very heavy blow, a defeat that hurts, but we must continue to have confidence in ourselves," Messi said after Argentina crashed to a stunning 2-1 loss in Group C

"This group is not going to give up. We will try to beat Mexico," he added. Argentina now have to focus on beating Mexico and Poland in their next group games

Messi lamented Argentina's shock second half capitulation against Saudi Arabia but said he was not surprised by the threat from opponents 48 places lower in the world rankings.

"It's a situation that this group of players has never been through, it's been a while since we suffered such a tough blow, we didn't expect to start like this," Messi told an Argentinian media outle.

Starting his fifth World Cup, Messi had opened the scoring with a 10th minute penalty and Argentina had three goals disallowed for offside in a free-flowing first half.

But in the second half, "in five minutes of mistakes that we made, we went 2-1 down and then it was really tough and we lost organisation and started punting the ball," he said

Messi said his team knew Saudi Arabia, despite being the second-lowest ranked team in the tournament, could hurt them.

Playing in his fifth and probably final World Cup, Messi has the weight of an entire nation's expectations on his shoulders.

One of the greatest players of all time, this may be his last chance to lift football's greatest prize, which his predecessor as Argentina's idol Diego Maradona did in 1986.