Day first broke into the world’s top 10 in June 2011, rising to world number nine after his runner-up finish in the U.S. Open of that year.
In February 2014, Day won his first WGC title, the WGC-Accenture Match Play Championship, which he would win for a second time in 2016. With his win in 2016, he joined Tiger Woods and Geoff Ogilvy as the only multiple winners of the Match Play title.
He went on to win his first Major tournament in the 2015 PGA Championship, finishing a record 20 strokes under par. He gained the world No 1 ranking two weeks later.
Source: Wikipedia