Carlos Carvalhal admits his gamble backfired as Swansea dropped back into the relegation zone after being thumped 4-1 by relegation rivals Brighton Hove and Albion.
A Glenn Murray double and goals from Anthony Knockaert and Jurgen Locadia brought the Swans 10 game unbeaten run in all competitions to a grinding halt.
The only goal for Swansea came from substitute Tammy Abraham with a 85th-minute consolation goal - a long-range effort which deflected in off Dunk.
It was a deflating defeat for Carlos Carvalhal who has been driving his team's revival after beating big name teams like Liverpool, and Arsenal.
The Swans manager admits his gamble to bring on attackers Andre Ayew, Luciano Narsingh and Tammy Abraham, with his side trailing, backfired.
Brighton simply exploited the gaps at the back.
Swansea are now in 18th place.