American Jordan Spieth faces "very tough competition" to return to the top of the world golf rankings this year, he said on Tuesday. The 23-year-old, who won the U.S. Masters and U.S. Open in 2015, started his campaign with a third-place finish in last week's Sony Open in Hawaii and lies fifth in the rankings. It's going to be a good year," Spieth told reporters at an event in Tokyo where he unveiled the "Spieth One" golf shoe which he has been working on with U.S. brand Under Armour. More...