LAHORE - Pakistan's bowling unit have been a dealt a major blow as in-form pacer Usman Khan Shinwari has been ruled out of the upcoming series against the West Indies.

Shinwari, the left-arm pacer, has been diagnosed with a stress fracture of the back in what is a career-threatening blow. The medical camp of Pakistan Cricket Board (PCB) has informed the team management that Shinwari will be out of action for at least six months as a result of the injury.

The 23-year-old bowler had stunned Sri Lanka with figures of 5 for 34 in just his second ODI two weeks ago.

He picked up the injury after second T20 against Sri Lanka in Abu Dhabi, and missed the final game of the tour - the landmark T20 in Lahore. Medical screening confirmed lumbar-bone stress in his back. He had struggled with the same injury in the early days of his career, in 2013, after making debut for Pakistan in T20 cricket.

He has sustained back injuries twice before and missed a major chunk of season of 2014-15 as a result. "It is disappointing but this [course of treatment] will give him the best chance of recovering as quickly as possible," Mickey Arthur, the Pakistan head coach, was quited as saying by cricinfo.

Shinwari was brought into the ODI side for the Sri Lanka series after Mohammad Aamir pulled out due to injury, and he made an immediate impact. His five wickets in the second game against Sri Lanka came within the space of 3.3 overs. The performance was a throwback to four years ago, at Gaddafi Stadium in Lahore, when he announced himself with five wickets for nine runs in 3.1 overs for Agriculture Development Bank of Pakistan.

Usman's injury is the latest in a string for Pakistan. Aamir recently missed the ODIs against Sri Lanka before returning for the T20 series. Usman adds to Arthur’s headaches as the Pakistan coach is already missing several players due to injuries. Left-arm pacer Rumman Raees missed the T20Is against Sri Lanka due to a wrist impingement, right-hand batsman Babar Azam is suffering from a groin strain and Imad Wasim is recovering from a knee injury. When asked whether he was concerned by this sudden spate of injuries, Arthur said: "A little bit, but a lot of them niggles just needed a bit of rest and that is why we have put such a lot of effort in working on our bench strength."

Now Shinwari will definitely miss the proposed West Indies tour of Pakistan, for whom the PCB is still waiting for a final word from Cricket West Indies (CWI) for a series of three T20Is.

The PCB has sent the proposed itinerary and the related plans to the CWI and the board is now waiting for the final approval. If the series go ahead the first Twenty20 is likely to be held on November 23. Another glitch in tournament is the factor that the West Indies would have been visiting New Zealand at the end of November so it is also a possibility that the West Indies board sent two different teams to Pakistan and New Zealand. If it happens, it may take some sheen away from the tour with lesser known players to make it to Twenty20 team and stars heading to New Zealand.  It is also likely that Shinwari may miss the third edition of Pakistan Super League and also a sure miss for New Zealand tour. Pakistan are scheduled to play New Zealand in five ODIs and three T20Is in early January, starting with a one-day practice match at the Saxton Oval in Nelson on January 3.