The South Africa left-arm spinner suffered the injury while celebrating dismissing Kyle Mayers during the second Test against West Indies and are will not feature in county cricket this summer
Middlesex are reeling from the news Keshav Maharaj will not be fulfilling his stint as an overseas player due to injury.
A ruptured Achilles suffered during South Africa's second Test victory over West Indies at the Wanderers leaves the left-arm spinner facing an extended period on the sidelines.
Maharaj appeared to pick up the injury while celebrating the dismissal of Kyle Mayers following a successful lbw review.
The 33-year-old, who has previously represented Lancashire and Yorkshire, was set to join up with the Lord's club from late April to the end of July.
It was due to include eight County Championship matches and the entire T20 Blast competition.
Pieter Malan is already confirmed to return to Middlesex (Harry Trump/Getty Images)
Pieter Malan is already signed on for the summer but Middlesex now face a race against time to fill the void left by his countryman.
"We are naturally extremely disappointed that Keshav will not be joining Middlesex this year after sustaining this freak injury and we are saddened to hear that he will face a significant absence from playing," said Middlesex director of cricket Alan Coleman.
"It goes without saying that everyone at the club wishes him a speedy recovery.
"For us to lose Kesh so close to the start of the new season is a blow, however, he wasn't scheduled to begin playing for us until late April, which buys us a little time to put Plan B into action.
"We will of course keep everyone updated on the situation regarding a replacement overseas player for the coming season."