ATLANTA (AP) — Georgia Tech gave up more than 40 points in six regular-season games before enjoying a postseason defensive turnaround that boosts hopes for next season.

The Yellow Jackets ended a streak of seven straight bowl losses with their 21-7 Sun Bowl victory over Southern California on Monday. The win followed a 21-15 loss to Florida State in the Atlantic Coast Conference championship game.

Coach Paul Johnson, who said he planned to evaluate his staff this week, had praise for the defense's best game of the season.

"I think we stayed away from giving up the big play and we did well on third down," Johnson said.

"I really think our guys played well the entire game. Other than the one drive we gave up, guys were playing fast and playing hard. They knew where to go and what to do; there wasn't a lot of thinking going on."

The late improvements on defense could help interim defensive coordinator Charles Kelly, who was promoted after Johnson fired Al Groh on Oct. 8.

Kelly tried to simplify the schemes so his players could depend on their instincts and react more quickly.

Kelly said his biggest impact "wasn't as much defense" as working to improve "where our players were at from a confidence standpoint, from the mental approach."

The Yellow Jackets had three interceptions against USC quarterback Max Wittek, who started as Matt Barkley was held out with a shoulder injury.

"Coach Kelly did a good job for us," said cornerback Rod Sweeting, who had an interception. "He kept preaching to just finish."

Georgia Tech scored more than 30 points in its first six wins before relying on defense for a change in the Sun Bowl.

"Coach Kelly has been doing a great job coaching the defense," said senior quarterback Tevin Washington. "Being out there seeing them make plays was great. The defense has been carrying us on the back of the season, so it was a good feeling."

Georgia Tech loses only six starters from the 7-7 team — three on offense and three on defense.

Quarterback Vad Lee could start in 2013 after playing behind Washington as a redshirt freshman.

Lee had 10 carries for 52 yards and threw a 3-yard touchdown pass to David Sims in the Sun Bowl.

Washington and Lee were two of five players to rush for more than 500 yards as Johnson's spread option attack ranked fourth in the nation in rushing yards. Washington led the team with 20 rushing touchdowns.

Another key loss is running back Orwin Smith, who had 682 yards rushing.

The offensive line loses only one starter, guard Omoregie Uzzi.

Kelly's defense held Southern Cal to only 205 yards.

"With the defense playing the way it was, it became a field position game," Johnson said. "We had chances to put them in bad spots when we were punting as well. The defense did a good job stopping them."

It made for a dramatic contrast to Georgia Tech's low point of the season, a 49-25 homecoming loss to Middle Tennessee State, which gained more than 500 yards.

Groh was fired after a 47-31 loss to Clemson the following week left the Yellow Jackets 2-4.

Georgia Tech was 5-3 with Kelly leading the defense, but progress was not steady. There were more defensive struggles, including a wild 68-50 win over North Carolina and a 42-10 loss to Georgia to close the regular season.

"As the year went along we had some better moments on defense and some not-so-good moments," Kelly said. "Definitely we would have liked to have been more consistent in some of the things we did, putting more quality quarters of defense together.

"The one thing I am very proud of is when bad things did happen to us, for instance we didn't play good at all in the first half against North Carolina, our kids didn't give up."

The defense loses three seniors — Sweeting, defensive tackle T.J. Barnes and defensive end Izaan Cross.

Among the defensive players expected to return are junior safety Jemea Thomas, who led the team with four interceptions, and sophomore cornerback Jamal Golden, who had three interceptions.

There are no seniors on the two-deep depth chart at any of the four linebacker spots. Quayshawn Nealy, Jeremiah Attaochu, Jabari Hunt-Days and Brandon Watts are expected to return as starters.