By Martyn Herman LONDON (Officialsportsbetting.com) – Reigning champion Jordan Spieth believes Tommy Fleetwood could be the biggest threat at next month’s British Open after a sensational second place at Shinnecock Hills last week. Spieth was a mere spectator as Englishman Fleetwood fired a magnificent final-round 63 to match the lowest round in U.S. Open history and almost snatch victory. Fleetwood had to be content with runners-up spot, one stroke behind American Brooks Koepka, but Spieth said he could carry that momentum into Carnoustie when it starts on July 20.