Scotland centre Alex Dunbar could miss the Rugby World Cup – after collapsing with suspected ligament damage to his left knee in training on Thursday . Dunbar had been named in the XV to face England in Saturday 's Calcutta Cup clash at Twickenham . But , running on his own just an hour before selection was announced this morning , he changed direction and his knee simply gave way . The damage is being scanned at a private hospital in Edinburgh , while a specialist will need to examine the images before making a final diagnosis . Alex Dunbar faces a race against time to be fit for the Rugby World Cup after injuring his knee at training . While Scotland coaching staff are hopeful that he may only have torn his cartilage , putting him out of action for around six weeks , there is a real fear that Dunbar has sustained damage to his ACL – which means up to six months on the sidelines . Matt Scott , who had been due to start on the bench , will take Dunbar 's place in the starting line-up on Saturday . Scotland centre Dunbar was due to start against England in the Calcutta Cup on Saturday . David Denton , Jim Hamilton and Dougie Fife will all start for Scotland against England on Saturday after Vern Cotter made five changes to his starting XV . Stand-off Finn Russell also returns to the Dark Blues line-up for the penultimate RBS 6 Nations clash at Twickenham after suspension ruled him out of the 22-19 defeat to Italy at Murrayfield two weeks ago . The Scots are desperate to restore pride in the Calcutta Cup meeting following three straight defeats to France , Wales and the Azzurri . Edinburgh number eight Denton - the only player among the incoming five not to have featured in this year 's competition - replaces Johnnie Beattie after shaking off the calf strain which has kept him out of action so far . Denton 's Gunners team-mates Fife - a try-scorer against France in round one - and Matt Scott replace injured wing Sean Lamont and centre Alex Dunbar , who are both ruled out with knee complaints . Russell , meanwhile , starts in place of Peter Horne while experienced Saracens lock Hamilton takes the place of benched forward Tim Swinson . Cotter said : 'Jim comes in and will bring his physicality and understanding of English rugby to our forward pack . 'It 's good to have Dave Denton back as he provides us with strong ball-carrying and strong defence . He 's also a very good lineout forward and will give us a bit more physical density against a big forward pack . 'It 's been tough on Finn to sit out and it 's great to have him back . He 's slotted straight back in to the structure we 're looking for . 'Finally , Dougie came on and played well against France and has had a couple of games with his club . 'We 're looking for him to bring his enthusiasm , energy and high work-rate , particularly in kick-chase and receipt . ' Tighthead prop Euan Murray , meanwhile , will equal Allan Jacobsen 's all-time appearance record for a Scotland prop when he collects his 65th cap . Dunbar , here showing his disappointment after Scotland 's loss to Wales , awaits results of scans on his knee . He will partner Alasdair Dickinson and fit-again Ross Ford , who has recovered from the back spasm suffered against Italy to start in an experienced front-row . Jonny Gray remains in the second-row to pack down with Hamilton , while Blair Cowan and Rob Harley start together for the sixth consecutive time in the back-row , alongside Denton . Captain Greig Laidlaw will again partner the returning Russell from scrum-half , with the back-line completed by Glasgow Warriors trio Mark Bennett , Tommy Seymour and Stuart Hogg . Hogg , Fife , Bennett , Scott , Seymour , Russell , Laidlaw . Dickinson , Ford , Murray , Hamilton , Gray , Harley , Cowan and Denton . Subs : Brown , Grant , Cross , Swinson , Beattie , Ashe , Hidalgo-Clyne , Tonks . Cotter added : 'This is a very important game . 'It will be played away from home at a very intense level and will allow us to assess further our ability to operate away from home in a hostile environment . 'Our focus , however , has been on ourselves and how we can perform better , by identifying the areas that we can control - like improving our skill sets and reinforcing our cohesion - to withstand the difficult times and also apply some pressure . '
Alex Dunbar was running on his own when his knee gave way on Saturday . The injury puts the Scotland centre in doubt for the 2015 Rugby World Cup . Scotland face England in the Six Nations for the Calcutta Cup on Thursday .