Defense was supposed to be Jacksonville's strength this season, the thing coach Gus Bradley could rely on while he sorted out the other side of the ball.

Through three games, the unit has been a liability.

The Jaguars (0-3) have allowed 466 yards a game and given up a league-high 119 points. They have experienced enough blown coverages, missed assignments and mental errors to last an entire season.

Players have seemed lost at times, leaving fans shaking their heads and coaches scratching theirs.

"Right now, we're just not playing at a high level," Bradley said Monday, a day after a 44-17 home loss to Indianapolis.

Jacksonville, which plays at San Diego (2-1) on Sunday, reached a low point in the first half against the Colts.

Indy scored on its first six possessions, taking a 30-0 lead before the Jaguars picked up their second first down. Andrew Luck had time to throw. Trent Richardson and Ahmad Bradshaw had room to run. And several receivers were left wide open across the field.

"It's a little frustrating," cornerback Dwayne Gratz said. "Until we correct those mistakes, teams are going to keep doing the same thing. So we need to stop the bleeding and progress from there."

The Jaguars rank 32nd in the league in total defense, coming in 25th or worse in 10 of 19 defensive categories.

Although they have done some things well — they have 10 sacks and held LeSean McCoy to 74 yards rushing in the season opener — those are few and far between.

Kirk Cousins, Nick Foles and Luck completed a combined 68 percent of their passes against Jacksonville for nearly 1,000 yards, with eight touchdowns and an interception.

The Jags insist it's not the entire defense out of sync, but rather one or two players out of position. However, it's happening on just about every play.

"We've got some guys doing the right thing and some guys not," defensive tackle Roy Miller said. "But when you're playing in the NFL, that kind of stuff gets you beat. It's a recurring theme that we need to get fixed. I don't know how many ways we can say it. We've just got to do it.

"When you look at the film, it looks simple: Just do your job. It sounds simple to say it, but I really think it is. Some guys are doing their job right and some are doing it wrong. That's a recipe for failure. Just do you job and at least give ourselves a chance to fight."

Bradley said he might consider personnel changes.

The quarterback switch could help.

Jacksonville's offense has been mostly stagnant since a first-half surge at Philadelphia in the opener. With Chad Henne at quarterback, the Jaguars had a league-leading 15 three-and-out drives in 10 quarters. When the offense can't stay on the field, it usually means the defense does.

And that's never good, especially for a team with little depth.

Bradley switched to rookie Blake Bortles at halftime Sunday, and Bortles' presence and plays lifted the entire team.

"When you keep playing defense and you don't get the reward of watching the offense do their thing, it does something to you," Miller said. "We like to think, 'Hey, whatever happens, we get paid to play defense.' But if you get in a rhythm of sitting down and going back out, it can frustrate you. I think what's promising is the second half. The offense was moving the ball and it just did something to the defense."

The Jaguars seemingly upgraded their defense in the offseason, bringing in pass-rusher Chris Clemons, run-stopper Red Bryant and backup lineman Ziggy Hood as well as linebacker Dekoda Watson. But even with added talent, the unit has been slow to gel. And now it could see more changes.

"Defensively we should be playing a lot better than that," linebacker Paul Posluszny said. "We're making mistakes. We're not playing together as a unit. We're not very consistent. We need to be much more consistent in everything we do. We're not trusting the guy next to us.

"We have such a strong desire to do well that we want to do a little bit more, and that's when things start to break down."

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