COSTA MESA >> One common theme running through the first four days of the Chargers’ training camp at Jack Hammett Sports Complex has been an overriding sense of optimism, a firm belief that an upgraded roster will produce results not seen since a 12-4 record and a playoff appearance in 2018.

“I think with the roster we have, the expectation is kind of like, ‘Let’s make the playoffs,’” wide receiver Mike Williams said Saturday. “Definitely, this year, with the added pieces we’ve got. We just control what we can control and that’s us coming here and every practice getting better.

“We don’t try to look too far ahead. We just try to keep the main thing the main thing, and that’s just to try to keep getting better and the rest will happen on its own.”

What’s more, Chargers coach Brandon Staley’s second season seems far different from his first in so many ways. There is a comfort zone that was absent in 2021.

“In better rhythm,” Staley said of his second camp with the Chargers. “There is just so much more confidence when you come to the practice field. I know who I’m working with, and it’s not just the players and coaches, it’s our entire sports performance team, it’s you guys (reporters).

“I think you have to have that full confidence when you come to the field and I think that allows you to be your best. It allows you to figure things out a lot better because there is so much to figure out. I’m excited about where we are and I expect us to continue to improve.”

There’s a long and uncertain road ahead, though.

The Chargers have miles to run before they can fulfill their heightened expectations. Their exhibition opener against the Super Bowl champion Rams is still two weeks away, their regular-season opener is more than six weeks away, and, as for the playoffs, they might as well be light-years away.

A good deal can happen between July and January.

Or February.

After all, the Chargers seemed to be ticketed for the postseason in 2021, when they faltered down the stretch and headed for an early vacation with a 9-8 record. They lost three of their final four games, including a disastrous overtime loss to the Raiders in the final week that doomed their playoff hopes.

“I mean, I didn’t like the way we finished the season, not getting a chance to compete in the tournament,” Staley said. “That stayed with me ever since I walked across that field in the last game. I liked the way we competed as a team in the last four games, but we were 1-3.

“That’s the facts.”

Increased competition

Defensive coordinator Renaldo Hill has noticed a change in camp after four days. Camp battles are more intense than in the past, with the competition heating up in the secondary, for example, even with All-Pro safety Derwin James sitting out while awaiting a contract extension.

“Urgency,” Hill said. “I feel like every rep is counting. I think that, maybe in the past, the players could have looked around and said, ‘Well, I don’t have that guy behind me. I can correct it.’ But that rep might get taken away from you if you’re not urgent and you keep repeating the same mistakes.

“We have to be more demanding as coaches and the players have to be more demanding with their responsibilities.”

Of the importance of competition for jobs, Hill said: “It’s everything. We know that in this league injuries happen. We need the next guy to be just as good as the guy he is replacing. On the back end (in the secondary), you have Michael Davis, J.C. (Jackson), you have ‘Zant’ (Asante Samuel Jr.), you have Bryce (Callahan), these are all top-quality starters who could be in this league.

“We’re going to push our guys. Nobody knows where it is going to happen because we’re not really putting a depth chart out (yet), so they know that the reps that they get here have to count.”