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.

Jason Dufner chips onto the 16th green during the second round of the PGA Byron Nelson Championship golf tournament Friday, May 18, 2012, in Irving, Texas. Dufner finished with a two-round score of 7-under-par (AP Photo/Tony Gutierrez)

Jason Dufner chips onto the 16th green during the second round of the PGA Byron Nelson Championship golf tournament Friday, May 18, 2012, in Irving, Texas. Dufner finished with a two-round score of 7-under-par (AP Photo/Tony Gutierrez)

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)

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Phil Mickelson hits from the 18th fairway during the second round of the PGA Byron Nelson Championship golf tournament Friday, May 18, 2012, in Irving, Texas. (AP Photo/Tony Gutierrez)

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Dicky Pride gestures during his putt on the fifth green during the second round of the Byron Nelson Championship golf tournament Friday, May 18, 2012, in Irving, Texas. Pride is 6-under going into the weekend. (AP Photo/Tony Gutierrez)

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Pat Perez takes a drop on the edge of the fourth green during the second round of the PGA Byron Nelson Championship golf tournament Friday, May 18, 2012, in Irving, Texas. (AP Photo/Tony Gutierrez)

Padraig Harrington, of Ireland, hits out of a bunker to the first green during the opening round of the PGA Byron Nelson Championship golf tournament, Thursday, May 17, 2012, in Irving, Texas. (AP Photo/Tony Gutierrez)

Matt Kuchar watches his shot from the third tee during the first round of the Byron Nelson Golf Championship tournament, Thursday, May 17, 2012, in Irving, Texas. (AP Photo/Brandon Wade)

HP Byron Nelson Championship - Round One

IRVING, TX - MAY 17: Phil Mickelson plays a tee shot at the third hole during the first round of the HP Byron Nelson Championship at TPC Four Seasons Resort on May 17, 2012 in Irving, Texas. (Photo by Darren Carroll/Getty Images)

HP Byron Nelson Championship - Round One

IRVING, TX - MAY 17: Todd Demsey plays a tee shot at the second hole during the first round of the HP Byron Nelson Championship at TPC Four Seasons Resort on May 17, 2012 in Irving, Texas. (Photo by Darren Carroll/Getty Images)

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