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Matt Kuchar reacts to leaving a putt short for birdie on the number three green during the second round of the Byron Nelson Championship golf tournament Friday, May 18, 2012, in Irving, Texas. (AP Photo/Tony Gutierrez)

Byron Nelson Championship

Jason Dufner chipped in from 37 feet, his fourth birdie in five holes, for a one-shot lead after two rounds of the Byron Nelson Championship in Irving, Texas.