49ers key matchup No. 3: Sopoaga vs. Sullivan

This is the first part in a series that spotlights three 49ers-Vikings matchups to watch Sunday, 10 a.m. (FOX-TV), at Mall of American Field.49ers NT Isaac Sopoaga vs. Vikings C John SullivanTale of the tape
Sopoaga (90): 6-foot-2, 330 pounds, ninth season, Hawaii
Sullivan (65): 6-foot-4, 301 pounds, fifth season, Notre DameNose tackle Isaac Sopoaga has been the forgotten man on the 49ers' starting defense through the first two games.That's because Sopoaga played only 15 snaps from scrimmage combined in the 49ers' season-opening victories over the Green Bay Packers and Detroit Lions.When the 49ers face the Minnesota Vikings on Sunday, that will change. Sopoaga will be asked to play a lot as a run-stuffer in the middle of the 49ers' line against a team that wants to run the football.MAIOCCO: 49ers defense faces first run challenge
"He'll definitely get more play than he's been getting based upon the way Minnesota plays," 49ers defensive coordinator Vic Fangio said.And how's that?"If you follow us, you know we're going to try to establish the run," Vikings coach Leslie Frazier said.Running back Adrian Peterson is rounding into top form after undergoing season-ending surgery to repair a torn ACL in his left knee in December. Peterson has rushed for 144 yards and two touchdowns on 33 rushing attempts in the first two games. Frazier suggested Peterson's work load could increase.MAIOCCO: Peterson says Willis should've been No. 2 pick
The Vikings love to run the ball behind center John Sullivan, who last season signed a five-year, 25 million extension. No team in the NFL has run as many plays straight up the middle as Minnesota. On 28 runs over center, the Vikings have averaged 4.25 yards per attempt.Sullivan, who played every snap in the Vikings' Week 2 loss at Indianapolis, went through limited practice Wednesday and Thursday due to an ankle injury. He is expected to play Sunday, and he'll have his hands full against a fresh Sopoaga.Sopoaga plays nose tackle in the 49ers' 3-4 scheme. When the 49ers go with extra defensive backs in passing situations, Sopoaga is the first player to exit the field.Finally, he'll get a full day's work. His job will be to tie up Sullivan, and perhaps even a guard, to prevent the Vikings' offensive line from getting to the second level to block Patrick Willis and NaVorro Bowman.If Willis and Bowman are able to make plays near the line of scrimmage in the run game, it means Sopoaga has done his job.