Munster wing Doug Howlett has been ruled out for the rest of the season with an ankle injury. It was confirmed today that the 33-year-old will have surgery on the ruptured Achilles tendon he sustained during Munster's RaboDirect Pro12 defeat to the Ospreys on Saturday. And Simon Zebo - the likely replacement for Howlett - suffered an ankle injury in today's training session at University of Limerick and left the complex on crutches. The surgery is due to take place tomorrow and is expected to rule him out for six to nine months. It means Howlett will miss all of Munster's Heineken Cup and RaboDirect Pro12 campaigns this year. The news further weakens the Munster backline ahead of crucial back-to-back Heineken Cup clashes against