Vern Cotter fears Alex Dunbar ’ s season-ending injury may also rule the star centre out of Scotland ’ s World Cup campaign . The Glasgow Warriors back suffered a major blow ahead of Saturday 's Six Nations clash at Twickenham when he damaged the anterior cruciate ligament in his left knee during Thursday morning ’ s training session . The SRU confirmed that he is ‘ out for the rest of the season ’ but , speaking before the result of scans on Dunbar ’ s freak injury were released , Cotter said ACL damage could mean up to six months on the sidelines and remove the 24-year-old from his World Cup plans . Alex Dunbar faces a race against time to be fit for the Rugby World Cup after injuring his knee at training . Scotland coach Vern Cotter fears Dunbar may not recover in time for the World Cup , starting in September . How England and Scotland will line up for Saturday 's Calcutta Cup clash . Visibly shaken by an incident that happened just a few hours before the team flew to London , Cotter now hopes his squad will be galvanised in the face of fresh adversity for Saturday 's Calcutta Cup clash . Explaining that Dunbar had been a key figure in his starting XV , Cotter said : ‘ We had named Alex to start at centre but he has perhaps done his ACL this morning . ‘ Alex did it on his own . A change of direction and his knee went out from underneath him . If it ’ s the ACL , that would be the World Cup as well . That ’ s not good . ‘ We ’ ll miss him in attack and defence . He ’ s one of our best line breakers and has been playing very well up to now . ‘ He is with some competent surgeons at the moment , he ’ s getting scanned . He ’ s understandably very upset about it . ‘ We ’ ve seen guys come back from an ACL before , so it ’ s just about when we get him back . But , if it ’ s the ACL , he ’ ll be six months . ‘ He was getting tested this morning . I went to see him during a break in training and he ’ s been whisked off with the pros . I will obviously talk to him again. ’ Dunbar , here showing his disappointment after Scotland 's loss to Wales , awaits results of scans on his knee . Matt Scott has now taken Dunbar ’ s slot for the England game . ‘ It ’ s an opportunity for Matt Scott , who was initially named on the bench , ’ said Cotter . ‘ You saw his two tries for Edinburgh last weekend , he is ready to step up . We ’ ve got an able replacement who has played well recently . ‘ We would dearly love to have Alex starting and then have someone like Matt come in and keep pace , bring physical intensity and presence to the game . But Matt has stepped straight in , and it means we ’ ll have to juggle the bench if we get injuries . ‘ I think it has tightened the group up – and that will be important when we play this weekend . We are playing what is probably one of the best teams in the world as they are preparing for the World Cup . The group adapts and moves on. ’ Coach Vern Cotter said the 24-year-old centre had played a key role in the Scotland XV . Dunbar ’ s withdrawal is one of five changes Cotter has made to his starting XV . Along with Scott , David Denton , Jim Hamilton and Dougie Fife all come in for their first starts of this Six Nations , while Finn Russell returns after serving his ban . Scott ’ s promotion sees Greig Tonks move on to a bench that boasts six forwards to only two backs – although No . 8 Johnnie Beattie has been told to prepare for playing a part in either unit . Cotter revealed : ‘ Beattie is a midfield replacement , emergency cover . He knows he could be marking ( England centre ) Billy Twelvetrees or he could be marking ( No.8 ) Billy Vunipola . ‘ I know he ’ s got a good boot on him . We know he ’ s a very skilful player . We want to have some physical density and some experience at the end of this match . ‘ So he and Adam Ashe , who has come back and has aggressive defence and is good on the ball , are there to put pressure on England . We want to stay close and finish this game with strength and experience . ’
Alex ##son was running on his own when his leg gave way on Thursday . The injury left the Scotland centre in doubt for the 2015 rugby World cup . Scotland beat England in the Six round for the challenge Cup on Saturday .