A "devastated" Garry Edwards has been forced to scratch Group 1 Paws Of Thunder (520m) favourite Double Twist after the speedster was found to be injured yesterday.

The Nowra pup was installed as an early favourite in markets for the $100,000-to-the-winner final at Wentworth Park tomorrow until she tore a back muscle.

Double Twist's scratching is another blow to a decimated Paws Of Thunder final after the midweek withdrawals of National Time and Allen Malik.

Reserves Punch One Out and Peter Rocket were guaranteed starts in the seven-dog field as a result.

A ballot will take place tomorrow morning to determine their boxes with three, five and seven all available.

Edwards had been on the verge of preparing Double Twist for her first Group 1 success after a flying heat win but was now resigned to her absence from the track for several months.

"I am totally devastated," he said.

"She has never been going better and had a perfect preparation leading into the Paws Of Thunder series and had drawn well for the final after a dominant heat victory.

"She was showing no signs of lameness at all but I knew the bruising [yesterday morning] wasn't a good sign and suspected she had injured her back muscle.

"She has only had a couple of minor injuries in her career and she will make it back to the track, so it could have been a lot worse."