Nine months ago, when Joe Gibbs was named to replace Jack Pardee as Redskin coach, quarterback Joe Theismann was ecstatic. It was, he said, like receiving an early Christmas present.

Theismann envisioned a season of joy, when he could function under his first offensive-minded head coach, where he no longer would be restricted, where finally he could blossom.

But even though he has produced three of the best passing days of his career, this has not become the season of Theismann's dreams.

His team has lost five straight games, the front office refuses to negotiate a new contract, he's being booed loudly at RFK Stadium, his leadership and consistency have been questioned and, for the first time since he became the Redskins' starting quarterback, he has a bona fide challenger, rookie Tom Flick, handpicked by management and waiting to replace him.

Gibbs says that nothing should be read into Theismann's removal in favor of Flick in the third quarter against the 49ers. But Theismann is aware of the reports, denied by General Manager Bobby Beathard, that management wouldn't mind seeing Flick as the starter.

"There is no way anyone in the front office is telling Joe Gibbs who he should play or who he shouldn't," Beathard said. "We think Tom Flick has an outstanding future, but Joe is our starter. And, yes, we expect to sign him to a contract next year."

But the fact that the Redskins chose not to extend Theismann's contract before this season began is an indication that there are lingering questions about his abilities. Before committing themselves to an expensive, long-term contact, the Redskins wanted to see Theismann, now 32, play a year under Gibbs.

The changes in Theismann since the start of training camp are particularly telling. Instead of remaining the outgoing, bubbly personality of years past, he is wound tight.

Before, he was able to keep his emotions under control in public. But already this season, he has had heated discussions with front office personnel and with a reporter, and he quit his job with television's Channel 7 after objecting strenuously to a critical commentary aired by that station. Away from the playing field, he is quieter and more introspective, although he has remained cooperative even in his lowest moments.

"I'm protective, I feel different," Theismann admitted. "Why? That's personal. Things are coming from a lot of different places. I really don't feel like I have to discuss the subject.

"I still enjoy what I'm doing, I still enjoy playing football. It's my life. You know how people jog to relax? I relax when I practice and play on Sundays. Some of my happier times are being involved in games.

"What's going to happen next year, no one knows. Football is still a game to me, but all the other things around it can be very childish and foolish. They seem like they are distractions. When you know you are going to be around and you can expect things, you can relax and enjoy yourself. When you don't know what's going on, things aren't the same."

He says he dismisses critics "because the criticism is coming from people who don't understand what we are trying to do. If I wasn't doing the job, if I was being inconsistent and not reading well, I believe I wouldn't be in the position I am. Until the coaches come and tell me I'm doing all these things wrong, I have to believe I'm not.

"How can I be considered inconsistent? I've missed on maybe eight or nine reads in five games out of 189 passes. I'd like to have some of the interceptions (nine) back, but I enter every game expecting to be perfect.

"I'm a better quarterback now than I was in 1978 or 1979. There's no comparison. Each year, you learn by experience, you get more comfortable. But we all are still learning this system. It's a great system, it has unlimited potential, but we are still in the thinking stage. Next year, we'll be in the react-and-play stage and things will be smoother. The differences between this system and one we were using is like night and day. It takes time for the transition."

Theismann leads the NFC in passing yards (1,375) and has had games of 281 yards, 318, 388 (career high) and 265 yards. All of his statistical averages compare favorably with his best season, 1979, except for interceptions. He had 13 that year in 16 games.

"The quarterback and the coach take the heat when you are losing," Gibbs said. "You can't blame Joe for the dropped passes and the injuries and penalties and everything else that has hurt the offense this season. He's made some reads and some passes we'd like to have back, but he's by no means the reason we are 0-5."

Theismann says he understands that the quarterback position "always gets too much praise when things are going good and too much blame when things aren't. But I've looked at the situation. Am I the problem? Am I a problem? I've got to face me, the heck with everything else. I have to look myself in the mirror.

"Am I the problem? I don't think I am. Nor do I think I'm creating a situation for coaches or anyone that is an additional problem than we already have. The quarterback position is one of the most forward, but also one of the most dependent on the team. I'm one of 45 guys on this team. We all have to worry about doing our job right, that's what will make things better."

But he also admits things have changed for him. Once he was the aspiring quarterback who heard fans chanting his name, asking the coach to put him in the game. Now they are calling for Flick.

"You think of when they were cheering and screaming for you, sure," he said. "You just have to hope you can bring them back. But they have a right to their opinion. They did then, and they do now."