Eden Prairie, MN -- (Sports Network) - Minnesota Vikings quarterback Tarvaris Jackson was diagnosed with a sprained right MCL on Sunday.

Jackson was injured when he was tackled by middle linebacker Ray Lewis on a scramble late in the first quarter of Saturday's 23-15 preseason victory over the Baltimore Ravens.

Last season, the 25-year-old threw for 1,911 yards with nine touchdowns and 12 interceptions in 12 games.

The Vikings have two remaining games in the preseason and will open the regular season against the Green Bay Packers on September 8.

If Jackson is sidelined for an extended period of time, Gus Frerotte will fill in as the starting quarterback.