CLEMSON -- Clemson football coach Dabo Swinney says the Georgia Tech defense is improved in its second year under coordinator Al Groh and that the Tigers might have to play in Atlanta at 8 p.m. Saturday without starting running back Andre Ellington.

Swinney announced after practice Thursday that freshman running back D.J. Howard will start in place of Ellington (left ankle), a former Berkeley High star who Swinney said is questionable after being limited in practice this week. Swinney said freshman back Mike Bellamy will also have his workload increase. Howard is averaging 6.7 yards per carry this season and rushed nine times for 86 yards against Auburn.

"I think (Ellington) will be a game-time decision as far as how sudden he is and how explosive he is in warmups Saturday night," Swinney said. "D.J. and Mike will carry the load for us early, and hopefully things will go well. … (Ellington's injury) is not anything severe, it's just one of those things that is getting better each day and needs a little more time."

Clemson figures to need its ground game since Georgia Tech is 10th in ACC play in run defense (193 yards allowed per game) but first in pass defense (170) and leads in total defense in conference play, allowing 344.6 yards per game.

Groh's 3-4 front and Cover 2 secondary scheme is designed to limit big plays in the passing game. The Yellow Jackets rank second in the ACC, allowing just six yards per pass attempt.

The Cover 2 scheme means two safeties are kept deep, providing deep safety help on receivers like Clemson's Sammy Watkins.

"It takes a while to go to the 3-4 scheme," Swinney said. "They don't give up many big plays because of the style they play with two deep back there. … It's a typical Al Groh-type of defense where you have to put long drives together."

A weakness in the Cover 2 is middle-of-the-field coverage, which could mean a big day for tight end Dwayne Allen, who has played effectively through a turf toe injury the last two weeks, catching 11 passes for 92 yards. Swinney said Allen's injury is not as severe as C.J. Spiller's turf toe injury in 2009. Swinney said Allen receives a pain-killing injection on gamedays.

He said it

Georgia Tech coach Paul Johnson on Clemson: "Clemson is probably the most talented team we've played since I've been here at Georgia Tech, at least in this stadium. They bring in a bunch of really good players and they're playing well, so it'll be a heck of a challenge."

Yellow Jackets can fly, too

Georgia Tech running back Orwin Smith (12.3 yards per carry) and receiver Stephen Hill (31.2 yards per catch) can produce big plays. After recording three games of 126 receiving yards or more in Georgia Tech's first four games, Hill does not have a more than 50 yards receiving in a game in the last four.