Georgia Tech quarterback Vad Lee scores one of his two touchdowns Saturday. The Yellow Jackets passed the ball just four times all day while generating 370 yards on the ground. (John McDonnell/The Washington Post)

The Maryland football team had rallied behind Shawn Petty throughout the week, insisting that the freshman linebacker-turned-quarterback was ready for his collegiate debut. Defenders checked on the offense during practice. Ricardo Young, a transfer quarterback sitting out the season under NCAA rules, tweeted daily about getting Petty ready, and wide receiver Stefon Diggs unleashed a rousing call to arms on Twitter after Caleb Rowe — the latest to fall in the Terrapins’ cavalcade of quarterback injuries this season — tore his ACL last weekend against Boston College.

But no matter how much resiliency these spirited Terrapins mustered, Petty was still Maryland’s fifth-string quarterback, a two-star defensive recruit who, just two weeks ago, was merely a spectator in sweatpants with the rest of the scout team during games.

And so the cheers came from 33,471 chilly, understanding souls in College Park during the Terrapins’ 33-13 loss to Georgia Tech on Saturday. They applauded when Maryland finally picked up a first down midway through the second quarter, or when Nathan Renfro mustered a punt longer than 20 yards, and were never louder than when Diggs hauled in a play-action slant across the middle, dancing and stretching across the goal line for a 16-yard score — Petty’s first career touchdown pass — late in the third quarter.

Petty also threw an interception and lost a fumble, finishing 9 for 18 for 115 yards and tacking on a 23-yard touchdown pass to Diggs as time expired.

“You just got to get used to the speed of the game,” said Petty, who played both quarterback and linebacker at Eleanor Roosevelt High School but was recruited to play defense. “That’s the biggest difference. Playing my first college game, when I was playing linebacker before this, the speed was a lot faster, so it took a while to get up to speed.

“I’m okay with it. I’m calm. Like I said before, I had time during the week, make sure I had my head right. Come Saturday, I was ready to play. We just didn’t execute.”

Maryland’s defense didn’t give Petty much help, allowing season highs in points, rushing yards and total yards. The Yellow Jackets’ triple-option offense ran for 370 yards, while the Terrapins (4-5, 2-3 ACC) managed just 259 total yards in losing their third straight game.

“You just don’t go out and line up at this level, only having seven practices, and think that everything’s going to happen the way you hope,” Maryland Coach Randy Edsall said. “Once he got settled in and we started to see what we could do with him, I think he showed his poise. The game still needed to slow down for him, but I thought he adjusted and moved the ball well in the second half.”

Maryland gained just 61 yards in the first half, entered the break behind 20-0 and lost leading tackler Demetrius Hartsfield to an apparent leg injury. The Terrapins even broke out the “Wildcrab” formation, with running back Wes Brown receiving snaps in the shotgun, but it accomplished little. Maryland needed Diggs’s game-ending score to avoid tying its season low in points. The first-year sensation has now set program records for receiving touchdowns (six), receiving yards (721) and all-purpose yards (1,774) in a freshman season.

A defense that entered the game ranked fourth nationally against the run produced punts on the first series of each half. But Georgia Tech (4-5, 3-3) scored three touchdowns in between, two resulting from Petty’s fumble and a 17-yard Renfro punt, as Maryland struggled to handle the Yellow Jackets’ unorthodox offense.

“It’s tough, because it’s not really our keys, stuff that a normal defense we get to go out and run,” defensive lineman Joe Vellano said. “It’s a totally different animal. They ran that well, and it’s hard to mimic it in practice. They changed up certain calls, went away from stuff they usually do. We had to adjust on the fly out there. Definitely is a tough offense.”

The road only becomes tougher. Maryland ends the season against No. 10 Clemson, No. 9 Florida State and 6-3 North Carolina, with no choice but to keep rallying behind Petty, who ended the game with a Hail Mary prayer into the end zone that Diggs somehow brought down from midair. The extra point was not kicked; the referee cited a lack of “competitive advantage.”

“I think we’ve got a really good group,” Edsall said. “I told them in the locker room, ‘We have to stick together.’ There’s going to be great things that will happen here. We all want them to happen today, tomorrow. But what we have to do is stick with the situation at hand.”