Player injury has prompted Head Coach Vern Cotter to recall three players from club duty to train with the national team this week.The delayed return of wing Sean Maitland from a shoulder injury, sustained in January, and ankle ligament damage suffered by back-row Alasdair Strokosch on Sunday, have necessitated the return of wing Tommy Seymour and lock Tim Swinson.The pair will join Glasgow Warriors club mate, stand-off Finn Russell - recalled as a precaution - and eight other national team players, for two days of specialist skills and strength and conditioning training at BT Murrayfield tomorrow (Thursday) and Friday, ahead of the next RBS 6 Nations Championship match against England at Twickenham (Saturday 14 March, kick-off 5pm).The 11 players will be unavailable for this weekend's Guinness PRO12 matches, though some 22 could feature for their respective clubs sides: six with Glasgow Warriors who face Zebre at Scotstoun on Friday night (kick-off 7.35pm), nine with Edinburgh Rugby for their trip to Treviso on Saturday (kick-off 6pm GMT), and a further seven at clubs in England and France, released in accordance with regulation 9 (World Rugby legislation on player release for Test duty).2015 RBS 6 Nations Scotland squad:Retained / rested: Mark Bennett, Fraser Brown (both Glasgow Warriors), Alasdair Dickinson (Edinburgh Rugby), Alex Dunbar (Glasgow Warriors), Ross Ford (Edinburgh Rugby), Jonny Gray, Euan Murray, Stuart Hogg, Finn Russell, Tommy Seymour, Tim Swinson (all Glasgow Warriors).Returning forwards: Adam Ashe, Alex Allan (both Glasgow Warriors), Johnnie Beattie (Castres), Hugh Blake (Edinburgh Rugby), Blair Cowan, Geoff Cross (both London Irish), David Denton (Edinburgh Rugby), Ryan Grant (Glasgow Warriors), Jim Hamilton (Saracens), Rob Harley (Glasgow Warriors), Moray Low (Exeter Chiefs), Alasdair Strokosch (Perpignan), Ben Toolis, Hamish Watson (both Edinburgh Rugby).Returning backs: Dougie Fife, Sam Hidalgo-Clyne (both Edinburgh Rugby), Peter Horne (Glasgow Warriors), Greig Laidlaw (Gloucester), Sean Lamont (Glasgow Warriors), Matt Scott, Greig Tonks, Tim Visser (all Edinburgh Rugby).