Stanford's Christian McCaffrey has Trojans' undivided attention

Stanford running back Christian McCaffrey (5) runs against Southern California during the first half of a Pac-12 Conference championship NCAA college football game Saturday, Dec. 5, 2015, in Santa Clara, Calif. (AP Photo/Marcio Jose Sanchez, File)Clay Helton remembers the turning point.

USC led Stanford by three points in the third quarter of the Pac-12 championship game last December.

It was less than 20 minutes from clinching its first Rose Bowl berth in seven seasons.

“I’ll never forget it as long as I live,” Helton said.

The Trojans’ defense was in man coverage when the Cardinal faced third down. Olajuwon Tucker, an inside linebacker, prepared to shadow Christian McCaffrey. Stomachs churned.

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