Brendon McCullum has been ruled out of Middlesex's NatWest T20 Blast quarter final against Northamptonshire on August 9.
The former New Zealand captain has been forced to withdraw from the match in Northampton because of an ongoing back injury that requires surgery.
He was suffering with back problems during the month he spent with Middlesex in June. His symptoms worsened during the Caribbean Premier League, where he was playing for Trinbago Knight Riders, and he informed Middlesex CCC of his unavailability once his commitments in the Caribbean had finished.
Middlesex CCC's Managing Director of Cricket, Angus Fraser, said: “I have been in regular contact with Brendon whilst he was at the Caribbean Premier League and was aware that he was struggling with his back.
“The short nature of a T20 means there is always the temptation to play someone when they have an injury but Brendon felt he could not do himself justice and did not want to risk letting the team down in such an important game.
“He has been having regular injections and dosing up on pain killers for some time just to get by, which is not particularly good for you.
“As a club we have not had a lot of luck with injuries in the past couple of weeks. Seven first XI players have been forced to miss cricket or play in discomfort for one reason or another.
“But we will travel to Northampton on Tuesday with an excited and extremely capable squad.
“These are the sort of games we wanted to be involved in when we discussed our goals at the start of the season and we will give it everything we have got."