Jonathan Dwyer made one of the plays of the day at Georgia Tech's Sunday practice, and he wasn't even carrying the ball.

Coaches mixed it up in a kicking practice, and Dwyer raced downfield like a sprinter while covering a kickoff and flattened a teammate as if a linebacker.

That flash of skills showed why coach Paul Johnson and staff are staking so much of their offense on the sophomore "B-back" from Kell High.

What is a B-back in Tech's new offense?

The B-back is the running back that lines up behind the quarterback, in the spot a fullback usually lines up in most offenses. Except, there's one big difference in this offense:

"He's a primary ballcarrier," said quarterbacks/B-backs coach Brian Bohannon.

"He's really a bigger version of an I [formation] tailback. You're looking for that bigger I-tailback, the 200-plus pound kids who can take it the distance."

Dwyer has speed. He averaged 5.3 yards per carry as a freshman, with a long of 65 yards, while totaling 436 yards and nine touchdowns. A little taller than 6-feet and around 222 pounds, he's hefty, too.

He's been more comfortable in practice than in the spring. "I see how this offense can work each and every time we run the ball," Dwyer said. "Me and [quarterback] Josh [Nesbitt] have a great connection now. It's something that's magical."

Getting down in a three-point stance for the first time, "since I was 10," after years of standing up as a halfback isn't the only change for Dwyer.

Much of his running will come between the tackles, although he'll get outside sometimes, too, like when he swept around the right end for a first down Tuesday.

More outside running will be left to A-backs. They typically line up outside the tackles, in slot positions, and are more involved as receivers than B-backs.

Which leads to future possibilities.

A-backs are typically faster in Johnson's triple-option attack, and Bohannon said, "They are usually not quite as big as the B-back, but we'd like them to be. They're more of a slot receiver, a guy that catches the toss."

Tech has more big backs now than in recent memory.

The B-backs behind Dwyer are Quincy Kelly (6-feet, 238) and Lucas Cox (6-feet, 238). They were fullbacks previously while Dwyer was a tailback, although Kelly and Cox have had turns recently working at A-back.

Freshman Richard Watson (6 feet, 225) and sophomore Anthony Allen (6-1, 225), but must sit out this season after transferring from Louisville, may factor at B-back in the future. If Watson redshirts, he and Allen will offer a big boost at B-back next season.

So might Dwyer move to A-back? He is, after all, the fastest B-back.

Let's not get ahead of ourselves.

"Possibly, if personnel dictated that," Bohannon said. "I don't think anything is locked in, but he's really done some good things at B-back."

For now at least, Dwyer's a B who might become an A. He's flexible, and sure looked it while covering that kickoff.

"If coaches Johnson and Bohannon need me to play A-back, I'll play A-back," he said. "If they need me to play right guard, I'll play right guard; anything to help the team out."