Peterborough's record signing Ryan Bennett suffered a knee injury during the 5-2 win over Oldham last weekend.
The former Grimsby centre-half came off at half-time of the win to be replaced by Gabriel Zakuani and is having medical checks to find out the severity of the problem.
Physio Peter Corder said: "Ryan sustained a lateral ligament sprain to his right knee on Saturday.
"It is in the early stages of his treatment at present.
"We need to concentrate on reducing the swelling around the area with ice, so we will see."