Khan landed in the water on the 18th at the Wentworth Club during the fourth extra hole, stumbling to a double-bogey 6, while the 20-year-old Manassero two-putted for par to wrap up his fourth career victory.
Khan, seeking to become the eighth PGA Championship winner over age 40, fired a 6-under 66 to charge in a share of the lead with Manassero and Marc Warren, each of whom posted 3-under 69s.
Warren fell out of the playoff on the first extra hole after his drive went into the trees on No. 18.
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