A stalemate at Old Trafford on February 24 saw the Reds surrender a valuable two points in their quest for Premier League glory, with Manchester City now well placed to retain their crown.
United were without a number of key players ahead of the clash and Ole Gunnar Solskjaer was forced to use all three of his substitutions after just 25 minutes, after injuries to Ander Herrera, Juan Mata and Jesse Lingard.
Jurgen Klopp's men failed to break down the home side despite their decimated squad and with only two matches now remaining of the 2018-19 campaign, that result could yet prove vital.
Liverpool are a point behind City heading into the final two weeks of the season and according to Scholes, who earned legendary status at Old Trafford over the course of a 20-year career, they missed a huge chance to beat his former employers.
The 44-year-old praised the two title rivals for their consistency before hinting the Reds could regret their display at United.
“What these two teams have done, right through the season, has been sensational,” Scholes told Premier League Productions .
“I won’t feel sorry for either of them but you’ve got to admire what they’ve done.
“When you look back, Liverpool’s biggest mistake was not beating Manchester United at Old Trafford.
“When you see how many players United were missing… they then had three injuries. Lingard came on and had to go off.
“Liverpool were really poor that day and you saw the difference the other night when City came to Old Trafford and were dominant and looked a really top team.
“Liverpool, ironically, could have lost the title at Old Trafford.”
Jurgen Klopp's side travel to Newcastle before hosting Wolves on the final day of the season, with a two-legged Champions League semi-final against Barcelona to negotiate in between .
City, meanwhile, face Leicester at home this weekend followed by a trip to Brighton and maximum points will see them successfully defend the trophy they won at a canter last year.