Glamorgan chief executive Hugh Morris says an injury to fast bowler Michael Hogan is "a blow" for the county.
Hogan, 33, injured a hamstring while playing for Western Australia recently and is due to arrive back in the United Kingdom on 1 April.
Glamorgan begin their championship season away to Leicestershire on 12 April.
"It's obviously a blow to us. he's a really important part of the team," said Morris.
"Our medical team will be assessing him when he arrives and continuing his rehabilitation."
Morris added: "With hamstring injuries it's sometimes difficult to tell [how long players are out for].
"Once we've had a good look at him we'll be in a much better position to assess that."
Hogan has been a crucial strike bowler for Glamorgan in the last two seasons, claiming 98 wickets in all competitions last season despite missing three weeks on paternity leave.
He suffered a hamstring injury playing for Western Australia in February and has been ruled out of the Sheffield Shield final against Victoria following a recurrence of the problem in training.