Adam Voges will not return to captain Middlesex in their bid to win the County Championship due to a hamstring injury picked up during Australia's tour of Sri Lanka.
Voges played in all three Tests of Australia's whitewash defeat, but Cricket Australia has blocked his return to Middlesex in order to recover from the injury in his home city of Perth.
The 36-year-old batsman had been due to return to the Championship leaders in time for their match against Warwickshire next week.
Middlesex are now exploring their options to bring in a replacement while James Franklin will continue on as captain.
"We are naturally disappointed that Adam cannot return," Middlesex managing director of cricket Angus Fraser said.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
"He is a fine player and a highly respected member of our squad. His presence will be missed.
"We have begun the process of seeing what other options may be available to us. As always seems the case, there is currently a lot of international cricket being or about to be played and international teams are understandably protective about their best players."
Middlesex lead the County Championship table by 26 points from defending champions Yorkshire, who have a game in hand.
Voges averaged 77.6 in six Championship matches at the start of the season.
"In Adam's absence we have a fine captain in James Franklin. James has done a brilliant job for Middlesex so far this summer and he will now continue to captain the club for the remainder of the season," Fraser said.
"Within our squad we also have plenty of strength in depth, as we showed during the County Championship win against Durham, which was achieved without an overseas player.
"Everyone at Middlesex CCC is excited by and looking forward to what should be a thrilling last month of the season."
