49ers key matchup No. 3: Aldon Smith vs. Chris Hairston

This is the first part in a series that spotlights three 49ers-Bills matchups to watch Sunday, 1:25 p.m. (CBS-TV), at Candlestick Park.49ers OLB Aldon Smith vs. Bills LT Chris HairstonTale of the tape
Smith (99): 6-foot-4, 258 pounds, second season, Missouri
Hairston (75): 6-foot-6, 330 pounds, second season, ClemsonBuffalo Bills lineman Chris Hairston, who made seven starts last season at left tackle, began this season as a backup. With an ankle injury to rookie Cordy Glenn, Hairston is back as a starter.RELATED: Three out for Bills
And his first starting assignment of the season comes Sunday. His task is to take on 49ers outside linebacker Aldon Smith, who leads the 49ers with 4.5 sacks. Smith has recorded 18.5 sacks in his past 17 games.The Bills will start two backups on the offensive line after Glenn and right guard Kraig Urbik exited last week's loss to the New England Patriots with ankle injuries.The 49ers are coming off a 34-0 victory over the New York Jets, and their front seven figures to pose all kinds of problems for the Bills."(It's a) great defense," Hairston told BuffaloBills.com. "They've got great D-linemen, great linebackers and they've done a great job as a defense. It'll take a little film study and lot of work on the practice field to be ready for them."But the O-line takes pride in playing good teams and doing what we can to assert our dominance. I'm sure this week is going to be a tough task with the guys we've got to go up against."The Bills' offense features a spread attack with quarterback Ryan Fitzpatrick getting rid of the ball quickly. Fitzpatrick has been sacked only four times in four games.In this battle of second-year players, Smith has a chance to exploit Hairston. Smith can make it difficult for Fitzpatrick to get the ball into the hands of his explosive threats in the passing game, such as receivers Stevie Johnson and Donald Jones, tight end Scott Chandler and running back C.J. Spiller.As an every-down player, Smith has done a good job of continuing to pressure the quarterback while also setting the edge in run defense. The Bills will run the ball more than most teams that feature three-wideout formations.
"That's the hardest thing for a guy that's transitioning from a defensive lineman to a linebacker position, outside backer in this case, is figuring out if it's a run or pass No. 1," 49ers defensive coordinator Vic Fangio said of Smith.
"And No. 2, they're not always coming forward. If it's a pass they've got to go backwards. So that's always new and uncomfortable for those guys. And that's really the biggest sticking point for those guys is figuring out if it's a run or pass and going backwards when they have pass responsibility."Smith has made a smooth transition this season from being a pass-rush specialist as a rookie."He's athletic enough and he's smart enough to learn the position and understand the position," Fangio said. "That's a good starting point."