Birmingham manager Chris Hughton felt luck deserted his side as they fell to a narrow 1-0 defeat against Europa League rivals Braga in their crucial Group H tie.
Striker Nikola Zigic saw his early penalty saved after Wade Elliott was wrestled to the ground in the penalty area by Ewerton.
The Braga defender then avoided a second yellow card just minutes later after bringing down Chris Burke in a promising position.
And Blues were made to pay the price shortly after half-time as Hugo Viana's 30-yard strike took a huge deflection off Curtis Davies and wrong-footed Boaz Myhill.
"I don't think we deserved to lose," Hughton said.
"I thought it was going to take a bit of brilliance or a little bit of luck for them to score.
"They got the one little bit of fortune that counted."
Speaking about the failure to send off Ewerton, Hughton added: "My first impression was that it should be a yellow card.
"I have to say I didn't realise it was the same player until one of my coaching staff made me aware of that. It was a definite yellow card.
"That being the case he then shouldn't have been on the pitch and certainly it makes it more comfortable for us against what is a very good Braga team with 10 men.
"I'm quite sure we would have had enough to then get a point from the game, if not to go on and win the game."
Birmingham now face a tall order to make the knockout stages, especially after Club Brugge's sensational fightback from 3-0 down to claim a 4-3 victory against Maribor.
Hughton's side host bottom club Maribor in the final round of fixtures. But their fate is out of their own hands as Brugge welcome already-qualified Braga to Belgium needing only a draw.
Braga boss Leonardo Jardim admitted his side were fortunate to ride the early storm. However, he felt his charges came back into the encounter and deserved the victory in the end.
"It was a bad beginning for us, the worst 15 minutes we've had this season," said Jardim.
"We were lucky Birmingham weren't able to score.
"We improved during the match, we gained victory from a very difficult game."