Sept 1 (Reuters) - Manchester United striker Wayne Rooney has suffered a head injury during training and is doubtful for Sunday's Premier League clash with bitter rivals Liverpool, according to British media reports. Rooney suffered a deep gash in his forehead during a collision with a team mate at the club's Carrington base on Saturday and needed stitches, the Sunday Mirror reported. The injury could also see the 27-year-old striker miss England's upcoming crucial World Cup qualifiers against Moldova and Ukraine, the paper said. England face Moldova at Wembley on Sept. ... More...