Kuchar was never headed during the championship match, and trailed for a total of only five holes during the entire five-day event at The Golf Club at Dove Mountain.
The win was his first World Golf Championship title and his fifth PGA Tour victory overall.
Mahan's streak of 169 holes without trailing at the match play event was broken on the fourth hole of Sunday's title round.
Jason Day took the consolation match with a 1-up decision over Ian Poulter.
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