Spieth held a four - shot lead with two holes to play .
Was eight clear of McIlroy , who struggled to a 77 and failed to record a single birdie for the first time in 81 major championship rounds .
Spieth held a four - shot lead with two holes to play and was eight clear of McIlroy , who struggled to a 77 and failed to record a single birdie for the first time in 81 major championship rounds .