Dallas Cowboys offensive coordinator Bill Callahan, left, is followed by rookie guard Zack Martin (70) during a rookie minicamp at the Cowboys' headquarters Friday, May 16, 2014, in Irving, Texas. (AP Photo/Tim Sharp)
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Dallas Cowboys offensive coordinator Bill Callahan, left, is followed by rookie guard Zack Martin (70) during a rookie minicamp at the Cowboys' headquarters Friday, May 16, 2014, in Irving, Texas. (AP Photo/Tim Sharp)
