"And Johnny, just like Robert, has that arm talent and intelligence to do that."
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Can he pull off the same feat in Cleveland now that Manziel has shown signs of being a quick study?
"Perception becomes everyone's reality, but Johnny has been here working his tail off day and night, doing everything we ask," Shanahan said. "He's really attacked it every day, done a good job even as each week gets harder as we throw a lot more at him.
"I've been very impressed."
Shanahan stressed that his starting quarterback decision will be "pretty simple." Whichever one moves the offense and puts points on the board in August will be under center when Week 1 rolls around.