NORTON - Jordan Spieth will regain his number one spot when the next world golf rankings are released despite missing the cut at the Deutsche Bank Championship. The US Open and Masters champion was assured of returning to the top of the rankings after Rory McIlroy failed to finish in the top 10 while Australia's Jason Day failed to win the tournament. The complex mathematical formula used to determine the rankings means Spieth will be back as world number one when the next rankings list is released. Northern Ireland star McIlroy finished his Deutsche Bank campaign with a five-under-par 66 on Monday, and said he was unconcerned by the nip-and-tuck world ranking battle. McIlroy told the Golf Channel he was more concerned with his form and moving up in the FedEx Cup playoffs standings.