Wearing No. 31, Petty will be asked to run, pass and hand off the football. His top priority, however, is to simply make it to the end of the game without getting hurt.
The Terrapins (4-4, 2-2 Atlantic Coast Conference) have already lost four quarterbacks for the season because of injury. C.J. Brown tore an ACL in August, Perry Hills ripped his ACL on Oct. 20 against North Carolina State and backup Devin Burns broke a foot in the same game.
Then freshman Caleb Rowe tore an ACL last week in a loss to Boston College.
So for the third time in three games, Maryland will have a different starting quarterback. Petty ran the option at Eleanor Roosevelt (Md.) High, but Edsall recruited the 6-foot-1, 230-pounder to be a linebacker at Maryland.
Not anymore. At least not for now.
"He played quarterback in high school, and I think he really feels he's a quarterback at heart," Edsall said. "I think he's really looking forward to the opportunity to go out there and play. He's excited, and we're excited for him. He wants to play really, really well. It wasn't like he's never played the position before."
Understanding the terminology and getting in sync with his receivers could prove troublesome for Petty, but he probably won't be bothered by the gravity of the situation.
"He is very laid back," Edsall said. "He never gets very high or low. He is a steady ship out there. He goes about his business. He is determined and focused. He's just looking for the opportunity and looking forward to take advantage of it."
Besides, it's not like Petty's teammates haven't been through this before.
"Our guys know how to handle it," Edsall said. "It's not all on Shawn. He's just one part of this team."
Two weeks ago, the Terps were 4-2 and unbeaten in the ACC. Now they're stuck in a two-game skid, starting a linebacker at quarterback and using a tight end (Brian McMahon) as his backup.
"Our big thing this week is we have to be very productive on first and second down," offensive coordinator Mike Locksley said.
Even though Georgia Tech coach Paul Johnson has enough problems of his own, he can sympathize with Edsall's plight at quarterback.
"I've never seen anything like it," Johnson said. "I'd have to think back through the years, where someone might be down to a fourth guy in a position for a week or two, but I've never seen that many season-ending injuries."
The Yellow Jackets (3-5, 2-3) would seem to be in good position to snap out of a skid in which they've lost three of four - including a 41-17 bashing at home last week by Brigham Young. But Johnson knows it's tough to take anything for granted, especially after watching his team lose to Middle Tennessee State by three touchdowns at home.
"Nobody just rolls out there and lets you win games. It's tough," Johnson said. "Our guys understand the importance of the game, and they also understand the importance of the game for Maryland."
Georgia Tech must win three of its last four to become bowl-eligible, and its remaining schedule includes road trips to Georgia and North Carolina. So the Yellow Jackets can't afford a slip up in this one.
"Certainly, this year hasn't gone as we have envisioned or how we would've liked," Johnson said, "but sometimes that happens."
This hasn't exactly been a predictable season for Maryland, either. Given how deep Edsall has dipped into his roster to fill the void at quarterback, he was asked who he would turn to if Petty and McMahon got injured.
"That's to be determined," he said. "You are jinxing me by asking me that question."