Richie Petitbon, the Redskin defensive coordinator, said yesterday he expects the St. Louis Cardinals to throw deep and often in the direction of free safety Mark Murphy.

The Cardinals no doubt will notice that Murphy was burned several times by long passes thrown by New England last week. Although he had one interception, Murphy was not at all pleased with his play.

"I just didn't have a good game last week," Murphy said yesterday. "The entire secondary unit didn't. We haven't played up to our capabilities the last two weeks, which is why we're working longer and harder in practice this week.

"I don't think we had any blown assignments against the Patriots. But there was hesitation at times. That split second of hesitation left us vulnerable. We can't allow that this week against St. Louis."

The Cardinals, without their two best receivers, beat the Redskins, 40-30, in the third week of the season. With Mel Gray and Pat Tilley rejoining Roy Green (23.4 yards per reception), the secondary cannot afford another poor performance.

"We just have to quit giving up the big plays," Murphy said. "With Tilley, Gray and Green in the game, the Cardinals can throw deep as often, if not more, than New England did. They're using Green the way they use Gray. I could end up covering all three in a given series. We'll have to mix our coverages more."

Coach Joe Gibbs said of the secondary: "We're counting on them coming through better than they have the last two weeks."

"Murph is to our defense what the quarterback is to the offense," Petitbon said. "Mark didn't have as bad a game as he thinks he did. But that's the way we want him to feel. It'll make him play better."

Fullback Wilbur Jackson, out nearly a month with an injured knee, practiced yesterday. Gibbs said Jackson is a "day-to-day case," as is offensive guard Melvin Jones, out more than two weeks with a sprained neck . . . The Redskins signed tight end Bob Raba, formerly of Maryland, the Jets and Colts.