Kelvin Bryant's season-ending knee injury means that rookie Brian Mitchell finally will get a chance to do what the Redskins originally envisioned him doing this season -- catching passes out of the backfield on third down.

Coach Joe Gibbs said Earnest Byner and Mitchell both will run some of Bryant's plays, but if Byner continues to get 30 carries a game, it's unlikely the Redskins also will throw to him 10 times.

That should mean more time for Mitchell, who already has surpassed virtually all expectations (his and the team's) for his rookie year.

"Hopefully I'll be in the game more and I'm excited about that," Mitchell said. "That's the main thing to me. I've run the plays all year in practice. The only difference is that KB ran them in games."

Mitchell was an option quarterback in college, but the Redskins noticed him while seeing him half-seriously running pass routes at an all-star game in Houston. When he was drafted, they believed he might eventually be their third-down specialist, but he also has rushed and returned punts and kickoffs with so much success, it's now only a matter of picking the spots to get him in games.

"I'm trying not to get excited," Mitchell said. "I want to stay relaxed and do the right thing. I'm the type person who, if I get excited, I make mistakes. This year has already been a lot more than I expected. I didn't expect to play as much as I have, and I certainly didn't expect to play quarterback {which he did in Philadelphia for a series after Jeff Rutledge and Stan Humphries were injured}. That was something I'll never forget." Picking Up the Pace

The Redskins traditionally have played their best ball in December since Gibbs arrived in 1981, and that has been no different this year. They're 3-1 this month and more impressive is how they've dominated both sides of the line of scrimmage. Over the past four weeks, they lead the NFL in rushing defense and are second in rushing offense. They've allowed only 59.3 yards per game on the ground and gained 188.5 per game. Only Philadelphia has done better on the ground this month. Walton Has Pinched Nerve

Safety Alvin Walton missed yesterday's practice with a pinched nerve in his neck. He's expected to play Sunday against Buffalo. . . . This will be the Redskins' latest regular season game in a nonstrike season. . . . Although it may seem the Redskins are running more than throwing, their run/pass ratio is about the same as last season's. They enter Sunday's game running 47.3 percent of the time to last season's 46 percent. . . .

The Redskins will say goodbye to retiring team statistician Bob Miller on Sunday. He has worked every home game since 1947 and became the chief stat man in 1961, when the team moved into RFK Stadium (then D.C. Stadium).