Cassio suffers calf injury

Adelaide could be forced to rush new signings Paul Reid or Scott Jamieson into the side to face Perth on Sunday after defender Cassio was struck down with a calf complaint.

Adelaide could be forced to rush new signings Paul Reid or Scott Jamieson into the side to face Perth on Sunday after defender Cassio was struck down with a calf complaint.

Either Reid or Jamieson could make their A-League debut for United with Cassio joining fellow Brazilian Diego on the injured list.

Coach Aurelio Vidmar said Diego was only ever an outside chance to start for the Reds but Cassio's unavailability hit hard.

"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," Vidmar said.

"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 felt his calf tighten up at training and an MRI scan on Tuesday morning.

Diego played in the first half of the club's internal trial last week but pulled up sore. Vidmar has vowed not to take any risks with his midfielder.

Versatile duo Reid and Johnson are among the players in the selection mix.