In 2000 he broke the championship scoring record held by Tiger Woods (18 under par) with a 23 under par 265.
Back on the other side of the Atlantic he won the English Amateur in 19.
He took victory after posting a final round 66, putting him one shot ahead of runner up, and fellow Englishman Simon Dyson.
He started the final round four strokes off the lead of Romain Wattel.
The couple lived a quiet life on a remote ranch in rural Arizona, where keen amateur horse woman Jocelyn competed in local equestrian events.
But after she abandoned an interior design course in 2010, the couple agreed to divorce. In the US he won three consecutive Pac-12 Championships (1998, 19).
This win vaulted Casey to a career high of 3rd in the Official World Golf Ranking.
In February 2015, Casey finished in a tie for second at the Northern Trust Open after losing in a sudden-death playoff to James Hahn.
Casey finished the tournament at six-under-par, tied with Hahn and Dustin Johnson.
He was also a member of Great Britain and Ireland's winning 1999 Walker Cup team, where he was only the third player in 77 years to record four victories without a single defeat.
Casey joined the European Tour in May 2001 and recorded a second in his fifth event and a win in his eleventh, the Gleneagles Scottish PGA Championship, ending that season 22nd on the order of merit and collecting the Sir Henry Cotton Rookie of the Year award.