(Photo credit: Action Images via Reuters/Peter Cziborra) Arsenal defender William Saliba is 'very doubtful' for France's World Cup opener due to a back injury, ESPN reported Monday. The 25-year-old center-back will undergo scans Monday to determine the extent of his injury, but the fear is he could miss the entire tournament in North America, per the report. Saliba played in 50 of Arsenal's 63 games a