Ranked 50th and 44th in the world respectively, neither country is widely fancied to topple Netherlands and Senegal to secure a place in the last 16 of the tournament.
However, victory in the curtain-raiser will massively boost their chances of doing so, while defeat would leave either with an even bigger mountain to climb heading into their final two group games.
Here, Sports Mole looks at how both sides have fared in the build-up to the tournament.
QATAR
As the hosts' domestic league has been on hold since mid-September, head coach Felix Sanchez has been able to hold in-depth training camps, with the most recent taking place in Marbella.
While there, Qatar have embarked on a surprising winning spree - beating Nicaragua, Guatemala, Honduras, Panama and Albania in successive warm-up games.
During recent months, too, friendlies against Canada, Chile and Jamaica have featured in the packed Qatari schedule, and though they lost 2-0 to fellow finalists Canada in October, a 2-2 draw with Chile saw them fight back to lead heading into the final 15 minutes - only Arturo Vidal's equaliser denied them a morale-boosting win.
Qatar kick off their campaign having not only played numerous exhibition games across the globe, but also reached the semi-finals of the 2021 Gold Cup, participated in the European World Cup qualifiers and made the final four of the Arab Cup this time last year.
They will, therefore, not lack competitive experience ahead of their exposure on the grandest stage of all.
ECUADOR
Ecuador's most recent outing saw them play out a goalless draw with Iraq last Saturday, meaning that they have now drawn each of their last three matches 0-0, also playing out stalemates with Saudi Arabia and Japan in the latter stages of September.
Ecuador's last win was a 1-0 victory over Cape Verde in a friendly in the middle of June, while they have not lost a single match since Paraguay beat them 3-1 back in March.
The team's last competitive match was a 1-1 draw against Argentina in March, with each of their last six matches being friendlies, including a 1-0 victory over Nigeria.
The fact that they have only scored once in their last five matches is slightly concerning, but Gustavo Alfaro's side have not conceded a single goal since the 1-1 draw with Argentina.