Sanchez defeated West Australian teenager Min-woo Lee after leading by two holes heading into lunch in their 36 hole final then losing that lead and trailing by two holes with three to play.
Matias, from the Royal Melbourne Golf Club, was clearly in trouble against the current US Boys Champion, Lee, who had fought his way back to take the lead with three holes to play but staged a remarkable fightback to win the final three holes and the match 1 up.
A holed putt from off the back of the green at the 16th swung the momentum back in Sanchez's favour and when Lee bogeyed the 17th (35th) the match was all square playing the last.
Lee would then find the fairway bunker from the tee at the 36th and took bogey while Sanchez was able to save par from short of the green and win the title.
Choi, who was the leading world ranked female golfer in the field and the individual winner at the Espirito Santo Trophy in Mexico in September, accounted for her fellow countrywoman So-mi Lee by a 4&3 margin and in the process earned a start at the LPGA’s Australian Women’s Open at the Royal Adelaide Golf Club in a month’s time.
Sanchez will advance his cause in the world amateur ranking and be guaranteed a start at the Australian Open at the Australian Golf Club in November.
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