Indianapolis spent the offseason trying to beef up its defense.

New coach Jim Caldwell changed coordinators, hiring longtime NFL assistant Larry Coyer. Team president Bill Polian selected bigger players in the draft and re-signed 296-pound defensive tackle Ed Johnson to help stop the run. And Coyer has revamped the system to take advantage of the Colts' speed and versatility.

So after three preseason games, fans want to know: Where's the new 'D'?

On Monday, two days after struggling to stop Detroit, Caldwell insisted the Colts are getting better, even if it hasn't been noticeable yet.

"Sometimes it's tough to tell," he said. "I can tell you this, we are improving. We do think we have some fundamental issues in terms of our tackling, which hasn't been where we'd like it."

A year ago, when Indy ranked in the bottom third in the league against the run, it allowed 4.2 yards per carry. In three preseason games, that number is down to 4.0. Opposing quarterbacks have completed 66.1 percent of their passes in the preseason, down from 68.4 percent during the 2008 regular season.

But it was the performance at Detroit that prompted the most concern. On a week that the Colts typically use as a regular-season dress rehearsal, the Lions gained 412 yards, ran 24 more plays than the Colts and scored two TDs.

Part of the explanation is the Colts were nowhere near full strength.

Indy was missing Johnson, cornerback Kelvin Hayden, defensive end Raheem Brock and middle linebacker and defensive captain Gary Brackett on Saturday. Cornerback Marlin Jackson, back from knee surgery, played in nickel packages against Detroit. Safety Bob Sanders, the 2007 defensive player of the year and the key to Indy's defense, is still out after offseason knee surgery and has not even practiced.

"It's been sort of mix-and-match, but tackling has nothing to do with that," Jackson said. "You've got to do your job. When you're learning a new defense, you're going to have some bumps."

In this case, maybe hidden agendas, too.

Though coaches and players have frequently discussed that they're incorporating more blitzes and more movement, the Colts have used mostly vanilla formations _ fitting with their traditional preseason model.

Clearly, though, Caldwell expected to see better results by now _ with or without his starters.

"You can lure yourself into a trap that way. We try never to think that way," he said. "We expect whoever is out there to play and play well. They should play up to our standards, which are lofty. We haven't done so consistently at this point."

Some of those who haven't measured up won't be around much longer. Indy waived four players Monday and still must make one more roster move before Tuesday's deadline, then trim another 22 players from the roster by Saturday. Three defenders _ defensive back Michael Coe and defensive ends Rudolph Hardie and Curtis Johnson _ were all placed on the waived-injured list Monday.

With time running short for those trying to win an NFL job, Caldwell is likely to give most, if not all, of his defensive starters an extended break Thursday at Cincinnati.

"There will be limited play for them (the starters)," Caldwell said. "We're just not certain what that 'limited' means. It means hardly any for some and a little bit for others."

Still, Caldwell expects things to get better.

He doesn't seem concerned with the prospect of going an entire preseason without having his 11 projected defensive starters on the field for a single snap. He'd rather they follow the Colts trend _ struggling in August before rolling through the regular season.

And the Colts are convinced that when the games count, they will get better.

"I think we've been inconsistent," Brackett said. "Minnesota was not a good week for us. Against the Eagles, we picked it up a little bit and last week, it was kind of back to the same things. It's a little tough (with injuries), but nothing's changed. Whoever is out there has to play football and I think we'll be OK."