By Tony Jimenez TROON, Scotland (Reuters) - Former European Ryder Cup captain Tony Jacklin, winner of the 1969 British Open and 1970 U.S. Open, assesses the chances of golf's 'Big Four' in this week's Royal Troon major. Jason Day (Australia) World ranking: One Major wins: One (2015 U.S. PGA Championship) Best British Open finish: Tied fourth in 2015 Jacklin's assessment: "Jason's a hell of a player. More...