WASHINGTON, March 28 (Xinhua) -- British teenager Andy Murray advanced to the semi-finals of the ATP Masters Series Sony Ericsson on Wednesday as he got an easy win over retired American Andy Roddick.

Murray led 5-3 after 29 minutes when Roddick pulled out. He had taken treatment before the final game in an ultimately vain attempt to continue.

As a result, the 19-year-old Scotsman, who ranks 12th in the world, advanced to a semi-final matchup against either Spanish second seed Rafael Nadal or Serbian teenager Novak Djokovic.

It will be the fifth semi-final of the year for Murray, who won at San Jose and lost in the Doha final as well and reached the semi-finals at Indian Wells and Memphis, where Roddick was his conqueror.

The injury is another setback for 24-year-old Roddick, who has a 21-4 record in 2007 and has reached four semi-finals this year, including the Australian Open, but has yet to claim a title.