Morrison suffered a shin injury early in Saturday’s Magners League win over Cardiff and, although he played 78 minutes, the problem has failed to ease.

Rob Dewey will make his first start at inside centre since his move from Ulster, with DTH van der Merwe coming in at right winger to make his first start for the club.

Cusiter was named in the team after recovering from the flu bug that forced him to miss the 21-5 victory against Cardiff, but he has now been struck down by a new illness.

Colin Gregor has been drafted back into the starting line-up for tomorrow’s Firhill encounter after deputising effectively against the Blues.

“Graeme picked up a bad leg knock last Saturday and wasn’t a well lad at the beginning of this week,” Warriors head coach Sean Lineen said.

“We’ve given him as much time as possible to recover because he was desperate to play but we’ve got to make the call at the end of the day.

“Rob Dewey has played international rugby at inside centre so I’m confident he’ll do a good job.”

Lineen added: “Chris has called off due a throat infection and no-one is more disappointed about him not playing than he is, but we’ve got to look after the health of our players.

“However, we can now bring in a fantastic player in Colin Gregor who had a great game in Cardiff and who thrives in Europe.”

Mark McMillan and Peter Horne have been added to the bench as a result of the changes.