The Red Devils are tipped to clinch the trophy due to their 12-point lead at the top of the table, but Valencia has claimed that fears over dropping points have crept in.
Sir Alex Ferguson's men lost the title in the dying minutes of the campaign last season to fierce rivals Manchester City on goal difference.
"We're a little worried. It has already happened to us," Valencia told Ecuadorian radio station Sonorama, according to Goal.com.
"Last year, having eight points with seven games to go we lost the league, and now we have seven games, 12 points and we don't want this to happen again. We want to finish off the two games that are coming as soon as possible, starting off in the right way and ending up victorious."
United dropped points on Monday by losing 2-1 to City, who reside in second place.