To the professional football team in San Diego, he is not so much a player as he is a policy. He is the halfback from Prudential, the Chargers' very own piece of the rock.

Mike Thomas is insurance.

He is the kind of security and protection a team thinking about the playoffs must have. So what if the premiums are high? So what if the Chargers were willing to pay Thomas what the Washington Redskins were not?

This is The Year in San Diego. This is the season the Chargers clearly are going for it.

So a richer, more relaxed Mike Thomas has arrived at training camp on the campus of University of California San Diego and immediately has assumed a low profile. He is not making any demands, not promising any 1,000-year season, not shouting about wanting to start.

"Hey, I know my role here," he says. "Lydell Mitchell is the No. 1 halfback on this team. I'm just here to try and help the team play better, to do what I can to help make us winners."

What Thomas does not say is that Lydell Mitchell also is the No. 1 question mark on this team. After having his knee examined in the offseason, the stylist Pro Bowl running back who arrived here from Baltimore last year developed a staph infection.

It left him unable to walk, let alone run, for a couple of months. And although he claims to be nearly 95 percent recovered now, Mitchell is working out only once, instead of twice, like everyone else in the first few weeks of camp.

That is why Thomas is here. That is why the Chargers invested a reported $150,000-per-year across five seasons to secure the services of a running back who encountered obvious problems with the Redskins last year.

"Yeah, there were things that didn't go too well last year," he admits. "But it's tough when you're playing out your option. It's just something you have to go through, I guess.

"There were some good feelings in Washington and some bad feelings. You know how it is."

Some of the bad feelings were expressed by Redskin General Manager Bobby Beathard after the Chargers negotiated the trade with Washington for, yes, the proverbial undisclosed draft choice.

Beathard said the only thing wrong with Thomas last year was his attitude.

"That's just an opinion," says Thomas. "Everybody has his own opinion. All I know now is that I'm happy to be here. I'm looking forward to the challenge.

"Last year, I didn't get as many carries as I had in the past. I tried not to think about that. I tried to concentrate on my blocking.

"Then I hurt my ankle for three weeks and there was a lot of controversy over that. A lot of people thought I could have come back sooner than I did."

There still is considerable controversy over Thomas in Washington. There still are people who think his main problem is a basic lack of competitiveness.

In football, the common term is "a dog."

So far, in the first few days of camp here, he has shown no such inclination. He has participated in every phase of practice. He appears eager and anxious on the field and composed and at peace off it.

"I know this team likes to use a lot of running backs," he says. "They like to go with a lot of different guys in there, and that's fine with me.

"I won't mind being fresher and not punishing my body as much. Every running back wants to gain 1,000 yards in a season. But I've already experienced that. Now, if I get that many, fine. But I won't be worrying about it if I don't."

He will not be worrying about his contract, either.

"I'm happy with what I signed for here, very happy," he explains. "It will be good not to have that hanging over my head, any more."

The Chargers seem just as happy to have him. Charger Coach Don Coryell, who used to face him when Coryell worked in St. Louis, puts it simply: "When a halfback like Mike Thomas is available, you'd be crazy not to try and get him."

Well, the Chargers tried and they got him. They paid a steep price, but they have their insurance. CAPTION: Picture, Mike Thomas