He'll miss Sunday's game at the Cleveland Browns.
Wallace took a vicious hit to the head from Sendejo in the first quarter, which drew a 15-yard unsportsmanlike penalty.
Wallace was ruled out with a concussion, and afterward, he was spotted on the sideline trying to find his helmet, searching in every equipment case. It had flown 15 yards from the spot of the hit.
NFL Vice President of Football Operations Jon Runyan issued the suspension Monday for a violation of Rule 12, Section 2, Article 6 (i) which states that "there shall be no unnecessary roughness. This shall include, but will not be limited to: (i) using any part of a player's helmet or facemask to butt, spear, or ram an opponent violently or unnecessarily."
In his letter to Sendejo, Runyan wrote: "The violation was flagrant and warrants a suspension because it could have been avoided, was violently directed at the head and neck area and unreasonably placed both you and an opposing player at risk of serious injury." Sendejo will be eligible to return to the Vikings' active roster on Monday, Oct. 30, following the team's Oct. 29 game against the Browns in London.