Geelong star Gary Ablett says the Cats know what went wrong against St Kilda last Friday night and are desperate to redeem themselves.

The reigning premiers put in a dismal first half in their qualifying final, then stormed home to fall four points short, forcing them into a sudden-death semi-final against Fremantle this Friday night.

"It was a disappointing loss, but I'm sure we'll bounce back this week, the boys can't wait to get into Friday night and we're really looking forward to it," Ablett said.

"We were just very disappointing in the first half, we've got to make sure we start the game better this week and fix up a few areas that I'm not going to go into, we don't want to give too much away.

"But I'm sure we'll start the game better and as I said, the boys can't wait to get into it."

Ablett said the Cats had identified what they did wrong in the first half.

"There were definitely some areas that we thought we needed to improve and we fixed them up in the second half, but by then it was too late."

The Cats' normally strong defence started terribly against the Saints, who scored almost every time they went forward in the first term.

Midfielder Joel Selwood and forward Steve Johnson were also among the stars who failed to have an impact before halftime.

While the Cats have been forced into a semi-final for the first time in four years, Ablett was confident they would not waste the chance to atone for an uncharacteristic finals performance.

"It's the reason we play the game, to win a premiership, so luckily enough we have the second chance and we're going to make sure we make the most of that," he said.

While Geelong are extremely short-priced favourites against Fremantle, Ablett said there was no danger of complacency.

"Every team's dangerous, especially every team that finishes in the top eight, they've obviously finished there for a reason and they've got some very dangerous players, we've got to make sure we shut them down."

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