Left-sided defender Cassio has a calf strain, while playmaker Diego is still being hampered by a hamstring injury.

Adelaide United Coach Aurelio Vidmar knew Diego was only an outside chance to be available for the first round, but Cassio’s absence is an added blow.

Cassio felt his calf tighten up at training last week, and an MRI scan this morning confirmed that he has a calf tear, ruling him out of the round one clash.

Vidmar said it was a disappointing setback for the squad less than a week out from kick-off to the new campaign. The United boss will now need to look at other options on the left hand side of the park for the match with Perth.

He said: “It is not something that we needed coming into the start of the season and I felt for Cassio because he has worked hard to get himself right during pre season after his knee injury.

“In saying that, it gives someone else an opportunity and I am sure that whoever comes in to do the job will perform and fulfil their role for the team.”

Cassio was looking forward to being playing in the first game of the 2008/09 season, the left sided defender searching for his first goal in the Hyundai A-League. The progress of his recovery will be closely monitored, but the early prognosis is that he could miss two weeks.

Diego played in the first half of the club’s internal trial last week but pulled up sore, Vidmar not taking any risks on the former Miami FC midfielder. The 28 year old made just one appearance in the 2008 Pre-Season Cup but Vidmar is hopeful to have him back in the main group by early next week.

His absence could open the door for new signings Paul Reid or Scott Jamieson to fill the void, the versatile duo able to play in a number of positions, including the heart of midfield.