Harrell figures to get plenty of playing time in the Packers' preseason opener at San Diego on Thursday night.
"At times, it's going to be different guys and young guys and guys that have never been in, and I think one of the most important things is just to make sure everyone's on the same page and we all know what we're doing and we're all going in the same direction and we all know what we're running," Harrell said. "That gives us a chance to be successful. So I think communication is going to be big for us. As long as we're all on the same page, I think we have a chance to be successful, because we have a lot of talented players."
Harrell threw 134 touchdowns at Texas Tech, a major college record that stood until Houston's Case Keenum surpassed it last year.
Undrafted out of college, Harrell got tryouts with the Cleveland Browns in 2009 and 2010, along with a year with the CFL's Saskatchewan Roughriders -- although he spent the entire season on the injured list. He joined the Packers in 2010 and 2011 as a member of the practice squad before signing to the active roster.
However, Harrell has yet to take an NFL snap outside of preseason play.
That's likely to change this year.
"He carries himself like a quarterback, and he acts like a quarterback," Thompson said. "And I think he thinks he's a quarterback. And he was pretty good in college. So far, he's doing well.
"Sometimes, it's a fine line between being a pretty good quarterback and maybe not good enough. I think our guys have done a good job of working with Graham and getting him farther along."
Copyright 2012 by The Associated Press