Cardiff Devils' Elite League hopes took a huge hit after Belfast Giants took the title race out of their hands.
Goals from David Rutherford, Mike Radja, Mike Forney, Mike Wilson and Adam Keefe were too much for Cardiff, who replied with two Joey Martin goals.
The Devils are two points behind league leaders Sheffield Steelers with two games remaining for both clubs.
Both sides host Nottingham this weekend, while Cardiff visit Manchester and Sheffield travel to Fife.
Devils chief executive Todd Kelman told BBC Wales Sport that the contest in Belfast was 'must win' for Cardiff.
"It is a truly must win game to stay in the hunt," Kelman said.
"We need the win to ensure we are level with the Steelers heading into the final weekend."
Saturday, 19 March, Nottingham Panthers, home, 19:00 GMT
Sunday, 20 March, Fife Flyers, away, 18:30 GMT
Saturday, 19 March, Manchester Storm, away, 18:30 GMT
Sunday, 20 March, Nottingham Panthers, home, 19:00 GMT