Valencia, nicknamed Superman, increased his record tally of goals for Ecuador to 37 and also became the country’s highest-scoring player in the World Cup as his double at the Al Bayt Stadium added to the three he scored in 2014.
A 16th-minute penalty on Sunday, nonchalantly stroked into the corner of the goal, was followed by an accurate glancing header, propelled with power past the Qatari goalkeeper, in the 31st minute.
Valencia, the only player in the 2022 Ecuador squad from their last World Cup appearance eight years ago, might well have scored the quickest goal in the opening game of a World Cup when he had the ball in the back of the net in the third minute but it was ruled out for offside after a VAR check.
"I thought it was a goal. I think Michael Estrada needs to do something about his toe nails because it was very tight," quipped Ecuador's manager Gustavo Alfaro of his player whose foot was judged offside.
"He's our greatest player. These goals today in the opening of a World Cup make him the best for all Ecuadoreans," said Victor López (about Valencia), an 18-year-old fan from the city of Ibarra in north Ecuador watching the game on a giant screen in a shopping mall.
Valencia, who was taken off for the last 15 minutes of Sunday's Group A game, has had a decade-long career in the Ecuador side, starting off as a winger but being converted to a striker in the qualifiers for the 2014 World Cup.
"I dreamt so many times about winning this opening match. This was a dream that I managed to score and help my team get the three points," Valencia said.
"We managed to score a couple of quick goals which helped us to get control of the game ... We think we can go very far and perform well."
He moved to West Ham United in a 12-million pound deal after the tournament in Brazil. After two seasons with the London side, he endured an uninspiring loan spell at Everton.
Valencia is now with Fenerbahce and in rich scoring form. His 13 league goals this season has put him top of the scoring charts in Turkey.
It was the fourth time in the last five World Cups that a player scored a double in the opening game of a tournament after Germany’s Miroslav Klose (2006), Neymar of Brazil (2014) and Russian striker Denis Cheryshev in 2018.
TOOTHLESS QATAR
Ecuador's second goal killed the Group A game as a contest and the second half was played at a slow pace, with many Qataris leaving before the end as Ecuador's fans chanted "Ole!"
Qatar looked largely toothless despite an enviously long time to bond and train together, including summer camps in Europe. Almoez Ali (26) had their best chance at the end of the first half, heading wide but then judged offside.
Mohammed Muntari (28) also fired over in the dying minutes.
Qatar's Spanish coach Felix Sanchez looked increasingly disconsolate watching his nervous-looking players misplace passes and allow Ecuador to outmuscle them easily from front to back.
"Maybe the responsibility and the nerves got the better of us," Sanchez said.
"There is no excuse, I want to congratulate our opponents Ecuador. There is a lot of room for improvement," he added. "We just have to let go, forget about it and be more competitive."
"We did not make more than four passes in a row and Ecuador played between the lines and the leading up of our attacks was not good. We also have to control the transition."
Sanchez said there was a lot to be learned from the match which will help his team prepare for the next one against African champions Senegal on Friday which will be even tougher.
The Spanish coach did not think the Qatar players' lack of participation in any competitive matches since the end of last season was a factor in their disappointing performance.
The Qatar Federation decided not to allow the players to feature for domestic clubs since the beginning of the season in order to devote themselves to getting ready for the finals.
"Preparation for the tournament was difficult as we played demanding matches in different weather and different atmospheres away from home," he said. "But of course, it's not like the World Cup" he added.
Both sides now have to play Senegal and three-time World Cup finalists the Netherlands, with Qatar's chances of qualifying from the group stage or even picking up points looking slim based on Sunday's performance.
At their fourth World Cup, Ecuador are dreaming of surpassing their best-ever previous showing at the finals when they reached the last 16 in 2006.
Their coach Alfaro will be happy that his players put aside the furore over defender Byron Castillo (24), left at home to avoid further controversy after they faced possible expulsion in a complaint by Chile over his nationality status.
"It was a great victory, especially as it was the opening World Cup match, so there's more pressure and tension," he said.
"You don't know how your team is going to perform. We are the youngest team in this World Cup. If we want to move to the knockout stage, then we had to win this match."
