Only NFL aficionados would be able to dissect the subtle differences between the Colts defense before and after defensive coordinator Larry Coyer's arrival.

But it can be boiled down to the basics.

He turned them loose.

He unlocked blitz packages that had been in the system but underutilized when Ron Meeks was in charge. No longer would the front four solely carry the pass rush - primarily ends Dwight Freeney and Robert Mathis, who, granted, are great at their jobs.

Coyer's style was to mix in more surprises, and the result could be seen more in freeze-frame than in statistics. Example: Middle linebacker Gary Brackett barreling over Ravens quarterback Joe Flacco in the playoffs.

Brackett, the captain of the defense, said Coyer stressed a new mentality from Day One.

“We met before the season, and we spoke about how we felt at times we weren't aggressive enough during the game, and he said that wouldn't be the case this year,” Brackett said. “To a man, he made sure that we understood.”

The most important part of Coyer's plan, Brackett said, was his follow-through on game day.

“It's one thing to plan five blitzes during the week and run one of them during the game. Guys kind of lose their luster,” Brackett said. “But when you put in five blitzes and you run all five of them, guys really get excited about that and they get their ears pinned back. And when your number is called, you want to go ahead and make a play.”

The new mentality freed Freeney and Mathis even more. Freeney ranked third in the league with 13.5 sacks, Mathis was 15th with 9.5 sacks and both were named to the Pro Bowl. Their numbers were more impressive considering they played a limited number of downs late in the season to protect their health.

Colts coach Jim Caldwell made two coaching changes, replacing the coordinator and special teams coaches, and there's little question that the addition of Coyer brought a new energy to the defense.

In two playoff games, the Colts have held strong Ravens and Jets running games under 100 yards rushing. In addition to the emphasis on blitzing and the threat of the blitz, the Colts showed toughness in short-down situations - including key stops against the Ravens in the regular season and a much-discussed stop by safety Melvin Bullitt on a fourth-down catch by the New England Patriots' Kevin Faulk.

The Colts ranked eighth in the NFL in the most important category - points allowed - which was up four spots from last season and could have been higher if they hadn't used backups in giving up 59 points in their final two losses to the Jets and Bills.

Caldwell praised his former coaches, pointing out they helped the Colts win the Super Bowl XLI, but he felt that the team needed a fresh approach.

“On defense, I just felt we wanted to be a little more aggressive, a little more of an aggressive style,” Caldwell said. “Larry and I have a history, a long history. And I've known for quite some time that when my opportunity came he'd be one of the guys, if he was available, that I certainly would try to attract. Thank God it worked out that way.”

Caldwell describes Coyer - who has coached at 11 colleges and with three NFL teams - as tough and hard-nosed.

“Everything he does exhibits that kind of aggressiveness, that kind of toughness,” Caldwell said. “He coaches that way, he studies that way, he prepares that way.”

The Colts defense thrived despite a number of roadblocks. Defensive tackle Ed Johnson, an expected key contributor, was released early in the season. Safety Bob Sanders, a former NFL Defensive Player of the Year, was lost for the season to injury, as was cornerback Marlin Jackson and linebacker Tyjuan Hagler.

The secondary spent much of the year without cornerback Kelvin Hayden and was forced to rely on rookie corners Jerraud Powers and Jacob Lacey.

And yet in 10-of-14 regular-season games (discounting the final two aberrations), the Colts allowed 17 or fewer points. They held the high-flying Arizona Cardinals to 10 points.

Freeney has mentioned on several occasions this season how freeing the defensive scheme has been. He called it the difference between the Colts dictating to an offense or letting an offense dictate to the Colts.

“As a defensive player, you always want to be in attack mode, aggressive mode,” Freeney said. “Go after whoever or whatever the play is. I think that definitely helps, but I think we do a good job of mixing it up. We definitely do a lot more this year than we did in years past.”

The defense has been helped by the continued strong play of its mainstays Freeney, Mathis, Brackett and Antoine Bethea, the huge improvement of linebacker Clint Session, and the solid play up front of Daniel Muir and Antonio Johnson. All-purpose lineman Raheem Brock seems to make a multitude of plays - most recently in his hustling downfield tackle of Baltimore's Ray Rice, forcing a fumble in the playoff game.

“We're just playing with confidence and a lot of speed out there, a lot of intensity,” Bethea said. “You see guys flying around. The coaches are doing a good job of keeping the game plan simple. There's not a lot of thinking out there. We're flying around and having fun.”

Thanks to Caldwell's decision and Coyer's delivery, the Colts defense was turned loose.