BBC Sport - Jason Day says he played 'hardest round of golf' in US PGA win
Hardest round I've played - Day
- From the section Golf
The world number five saw off a chasing pack that included Masters and US Open champion Jordan Spieth, who finished three shots back in second place and now moves up to number one in the new world rankings.
South African Branden Grace was third on 15 under and Justin Rose of England finished fourth on 14 under after his challenge faded with a double bogey on the 13th.