Marcus Williams probably was seeing a possible pass interference come about as he was running right on Diggs as the ball was approaching. If it was pass interference on the spot then the ball would have been on the 35 yard line and the Vikings could kick a FG to win it with no time remaining
“Marcus Williams probably was seeing a possible pass interference come”
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Good point, maybe he was trying to show that “his hands were clean” of interference.
He could have let him catch it. Time had run out. He didn't have to risk a pass interference.
Time management by Saints was suspect also. They should have run more off the clock before kicking there last field goal.