JACKSONVILLE – Gus Bradley's focus Monday was clear.

And although the Jaguars' head coach remained characteristically positive on many fronts, on a couple of topics he was notably pointed.

One was that he does not accept losing.

"That's not what we're about," Bradley said a day after a 33-14 loss to the San Diego Chargers at EverBank Field moved the Jaguars to 0-4 for the 2014 regular season.

"We're not light on losing," Bradley added. "We are all highly competitive but it's just that strict mindset to go to that we're not playing our best right now so we can't think about anything else. We haven't accomplished playing our best yet. Let's do that then we will see what happens."

This, too, was clear from Bradley Monday:

While the defense improved in some areas – and while specific players played well – the secondary and the accompanying pass coverage is not playing nearly well enough.

Bradley, in his weekly next-day press conference at EverBank Field, said while the team improved in areas such as tackling – and while it overall did a good job covering Chargers tight end Antonio Gates – the corners continue to struggle to challenge routes effectively.

Bradley said while the defensive philosophy emphasizes corners "staying on top" and not allowing the big play, that approach can't come at the expense of not challenging the pass.

"I think that's what we've got to get our corners to understand and see if we're capable of doing that," he said.

That was a theme of Bradley's last week following a 44-17 loss to the Indianapolis Colts, and Bradley said those troubles continued against the Chargers.

"I think that we're not challenging throws," Bradley said. "I think they had forty attempts and (the Jaguars had) one PBU (pass breakups). That's not how it should be. You should have more pass breakups.

He added, "I just want to make sure that they're not 'my job is to stay on top, I did it and it's good.' That's not good enough. What's good enough is you challenge throws, you stay on top and you compete all the way through the end of the play."

Chargers quarterback Philip Rivers completed 29 of 39 passes for 377 yards and three touchdowns and no interceptions Sunday, with his touchdowns coming on passes of 43 and 47 yards to wide receiver Eddie Royal and 24 yards to wide receiver Malcom Floyd.

Bradley also said the Jaguars must improve in explosive plays allowed, third-down percentage and takeaways. After forcing three turnovers in the first half of a Week 1 loss at Philadelphia, the Jaguars haven't forced a turnover in 14 quarters.

"I think those are three issues that we need to take a look at," Bradley said.

The Chargers converted 9 of 16 third downs into first downs, with four of the receptions on those plays 20 yards or more. Two of Rivers' touchdown passes – the 43-yarder to Royal and the 24-yarder to Floyd – came on third-and-10.

"The explosive plays went into the third downs and that's not a good match," Bradley said.

Bradley said there were positives defensively, particularly in the area of tackling, sacks and red-zone effectiveness. The team reduced missed tackles from double digits the past two weeks to seven, sacked Rivers twice and held the Chargers to no touchdowns in four red-zone opportunities.

"I think we look at the positives but we don't want to run away," he said. "In order for us to take the next step we have to do something about this area."

Also around the Jaguars Monday:

*Bradley said review of the video showed that rookie quarterback Blake Bortles had a good day in his debut as a starter. Bortles completed 29 of 37 passes for 253 yards and a touchdown with two interceptions. While Bradley said Bortles had perhaps five or six mental errors, overall that "was not too bad." Bradley added, "He got into a rhythm so it's good. What can you say? He completed 78 percent his first debut. He is frustrated that he threw the couple of interceptions but we will continue to grow with him." …

*Bradley as was the case Sunday said he had a better feeling after the Chargers loss than the week before against Indianapolis. "Last week it was tough on us," Bradley said, adding that he worried about the team's "spirit" late in the loss to the Colts. "This week I didn't sense any of that. They were going after it, competing all the way through and I felt like we finished. We finished because of how we went and played all the way through. We just didn't make enough opportunities." …

*Bradley said he sees signs of improvement in the run game. The Jaguars rushed for 85 yards on 25 carries, with running back Toby Gerhart rushing for 32 yards and a touchdown on 10 carries and running back Denard Robinson rushing for 25 yards on nine carries.  "It appears to me watching it with the offense that our offensive line is becoming more cohesive," Bradley said. …

*Bradley said while the team feels very strongly about Gerhart coaches will continue to look for ways to get Robinson more opportunities. …

*Bradley called the game a good one for the special teams. Running back Jordan Todman returned six kickoffs for a 29-yard average and the Jaguars limited Royal to two yards on one punt return. …

*Bradley said left tackle and left guard Zane Beadles each played better against San Diego than the previous week against the Colts. "They improved," he said. "The challenge was 'you're not going a good enough job with the one-on-one's let's get this better.' It's not just talk. …We saw improvement by those guys so it was a good sign."…