He was 21 for 29 to go along with four passing touchdowns and two interceptions in the game.
On the day the former SC product produced three tackles and two pass defenses to go with the two interceptions.
Keenum threw a career-high four touchdown passes in the second and third quarters for a 35-17 lead.
And with that, the Vikings improved to 7-2 on the season, on a day when their defense was far from ideal. The Redskins were losers in their second straight home contest, with a sound 38-27 loss to the Minnesota Vikings.
One of the few bright spots in the contest was the play of safety D.J. Swearinger. Harris is the cousin of Los Angeles Chargers wide receiver Keenan Allen.
Harris was brought up from the Redskins' practice squad Saturday, and wasted little time making his coaches look like geniuses. The play was ruled out of bounds, but the Redskins challenged and replay showed Harris came down inbounds for the touchdown.
Vikings DE Everson Griffen (foot/back) is inactive for Sunday's Week 10 game at Washington.
After his touchdown reception, Diggs jumped on padding of the goal post to give it a big hug.