With all due respect to the Netherlands - and boy, did they earn some respect with their 5-1 spanking of Spain - this was the first major shock of the tournament.
As with Friday night's Group B shock, all seemed to be going to form early on with the favourites going in front from the penalty spot. But then, it all went very different...
As if to underline this was no walkover, the first 10 minutes were cautious and even. Uruguay shaded the early stages with 51.5% possession.
By the 20th minute it was obvious that Uruguay were going long more often, but less successfully.
Even so, the favourites took the lead in the 23rd minute, Edinson Cavani scoring from the spot after Diego Lugano was fouled.
Satisfied, Uruguay sat back for a while and tried to turn Costa Rica round with long balls: the Celeste had fewer passes overall but twice as many in the top third, often verticals.
By half-time Uruguay were 7-3 up on shots, with Costa Rica yet to hit the target.
With 52.3% possession, Uruguay were marginally ahead on passes...
...but were much more penetrative, completing 31 passes in final third.
But it all turned round with two goals in four minutes from Joel Campbell's sharp finish and Oscar Duarte's brave header.
Indeed, Costa Rica were much better at getting into the box...
...and dominated the second-half shot count.
As Uruguay threw men forward it took them little more than half an hour to complete more attacking-third passes than in the first half...
The second-half pass count shows that Costa Rica were happy to let Uruguay have the ball.
Indeed, the Celeste totalled twice as many final-third passes - to no avail.
The clearance map shows the Costa Ricans were quite happy to bat Uruguay away.
Despite having less of the ball, Costa Rica outshot Uruguay 13 to 9, and 4 to 3 on target - meaning Fernando Muslera only made one save.
Facts and figures
- Costa Rica scored more than twice in a World Cup game for the first time (this was their 11th match overall).
- Uruguay have now gone 6 opening games without a win, last winning their first match at a World Cup in 1970.
- Uruguay have been responsible for 2 of the last 3 red cards at World Cups (Suarez vs Ghana in 2010 & Maxi Pereira today).
- Uruguay have conceded 3 goals in each of their last 3 games at the World Cup.
- Uruguay have not come from behind to win a World Cup game since 1966.
- Costa Rica scored with 3 of their 4 shots on target, all of which came in the second half.
- There were 38 fouls in this game, more than at any other game so far at Brazil 2014.
- After 6 games at this World Cup there have been 22 goals compared to only 8 at this stage in 2010.
- The last 26 penalties scored in normal time at World Cups have been right-footed.