Vincent Tobias Evans of the Chicago Bears has an appointment with destiny on Sunday. As he tries to sleep tonight, he may be wondering why his first regular season start had to be against the Dallas Cowboys, the champions of the National Football Conference. And in the NFL's nationally televised game (4 p.m., EDT).

It may be slightly comforting for Evans to remember that the last time he was seen by millions of televiewers, he led Southern California to a 14-6 victory over Michigan in the Rose Bowl and was acclaimed as the game's most valuable player.

In giving the nod to Evans over Bob Avellini and Mike Phipps, Coach Neill Armstrong was aware of the risk. "We must be ready to pass-block," Armstrong said, "because Dallas does a good job of blitzing."

Evans is a veteran of only 14 plays in 1978, his rookie season, and seven passes this season against Minnesota.

Why is Armstrong putting such a burden on Evans? Because the coach figures Evans can do things with his whip hand and young (24), fast legs that Avellini and Phipps can't.

Armstrong thinks the Bears are ready for and need a new dimension to an offense that has consisted mainly of Walter Payton left, Walter Payton right and Walter Payton up the middle.

Evans is a robust 6-foot-2, 210 pounds, sprints out with the dash of a fellow who can run 40 yards in 4.6 seconds and "seems to give the team a lift when he enters the game," Armstrong said.

The Bears know that Evans may be nervous. That was one of his problems while growing into the opportunity -- as soon as he would feel pressure from a rush he would roll out of the pocket. But the Bears have been through that.

Payton was so nervous his first year with the Bears that he hyperventilated and had to sit down to overcome it.

Evans demonstrated a quantum jump in poise in an exhibition game this season and said afertwards, "I found the Lord over the winter. I learned how to be calm and now I'm relaxed."

There was an absorption of technique, too. He used to pass at the same speed every time, as if he were trying to throw the ball through the receivers.

In the exhibition against the New York Jets he threw three touchdowns in the second quarter. The first was the usual bomb, for 70 yards to wide receiver James Scott. On a second touchdown for Scott, he took something off the ball and lofted it classically over a defender on a six-yard play.

It was the third scoring throw that signaled Evans' arrival. He waited patiently for the third choice of a receiver to get open, and hit tight end Mike Cobb with a 22-yard pass on a crossing pattern, for a touchdown. In that 21-point quarter Evans hit on nine of 12 passes for 165 yards.

So why didn't the Bears start Evans against the Green Bay Packers in the regular season opener and against the Vikings last week?

Because the Bears realized they had to win the two games against their Central Division rivals and could do that with their defense, which they pretty much did. They defeated the Packers, 6-3, and the Vikings, 26-7.

Phipps started against the Vikings but was coming off an attack of the flu and was too weak to continue in the second quarter with the Bears behind, 7-3. Enter Evans.