Columbus made mathematically sure of a playoff spot with a 3-0 win over New England, which will set a franchise record for fewest wins in a season.
Mendoza opened the scoring after half an hour. Darrius Barnes lost track of a long ball bouncing on Gillette Stadium's turf and the Peruvian striker exploited a half-chance to lash home first time.
Another long ball led to Duka's goal, with goalkeeper Will Hesmer starting the move from his box. The 22-year-old scooted around Kevin Alston and tucked a low narrow shot inside the far post.
Mendoza doubled his tally a few minutes later. Another one-timed left-footed blast capped off a skidding Emilio Renteria cross. The goal was Mendoza's 13th of the season, one off the league lead.
"New England had their hands full with these two guys," Crew coach Robert Warzycha of Renteria and Mendoza. "It was a beautiful finish by Mendoza, and the first one also. That's what he does to you."
The loss condemns the Revs to a club record fewest wins in a season. Columbus is third in the East, one off the lead, with one match remaining.
"I think we are going to go to win the Eastern Conference," Warzycha said. "We have a game in Chicago, and we have some momentum."
Additional reporting by Justin Churchill