Its group in the Asian Cup — with regional rivals Iran, Bahrain and its opening-game opponent, United Arab Emirates — was regarded as tough but passable. It still is, but progressing to the knockout stage is looking much more difficult after a 4-1 defeat in the opening game here in Canberra.

On a cool Sunday evening, against perhaps its biggest regional rival, Qatar took the lead thanks to an exquisite lob from its talented attacker, Khalfan Ibrahim. But then Qatar’s defense and goalkeeper struggled and fell apart as the talented Emirates team scored four times. It could have been worse.

After the game, U.A.E. midfielder Khamis Esmail remarked that the game had been “easy,” sentiments echoed by Michael Cockerill, a respected soccer columnist for The Sydney Morning Herald. “Qatar was surprisingly poor,” Cockerill said in an interview. “I was a little surprised at the technical level of some players. I expected better.”

Against Iran, Qatar will need to show that it just suffered a bad stretch of 90 minutes after 18 months of success. “The buildup to this suggests that Qatar knows how to win and the good results will have increased confidence,” Cockerill added. “It is just a question of how much that confidence has been damaged by the loss to U.A.E. To win the Asian Cup though, they have to improve by 300 percent.”

For Qatar defender Mohammed Musa, the Asian Cup is a chance for the team to grow. “Our group is a young group, and we are trying our best to gain experience by playing against these big teams in Asia,” Musa said. “We hope as we work toward the World Cup qualifiers that we can get better levels of experience from each game we play.”

A loss Thursday in Sydney to Iran, the group favorite, would almost certainly end Qatar’s chances of reaching the knockout stage. Iran, led by the former Real Madrid coach Carlos Queiroz, picked up a comfortable win over Bahrain in its first Asian Cup game.

The Egyptian journalist Abdelaziz Abuhamar of the Qatari newspaper Estad Al Doha said that short-term setbacks would not deflect the team’s long-term ambitions. “To qualify for the 2018 World is a must for Qatar,” Abuhamar said. “The strategy is to do well in each and every tournament. The Asian Cup is an important point for them to know that they are doing what it takes to qualify for the World Cup.