Neil Warnock was 'biting [his] tongue' after a hugely frustrating afternoon at the Liberty Stadium.
Boro were denied a wonderful Marc Bola goal - or a penalty of their own - before Sam Morsy netted a deserved equaliser.
And the disappointment was confounded when the home side were awarded and scored a spot kick to win the contest in stoppage time.
"I enjoyed the way we played, we tried to get in behind," Warnock said.
"I can't fault the lads for effort, but everything that could went against us today."