Rooney left the Premier League last year after 16 illustrious seasons with Everton and United respectively.
During his time at Old Trafford, he became the club's all-time record goalscorer with 253 goals in 559 games across all competitions and won five league titles.
And with his affiliation to Merseyside being that of the Blue half, the idea of Jurgen Klopp's side possibly breaking their 27-year title drought is something that genuinely frightens the 33-year-old.
"It's a great reason to be out the country when those two are going head-to-head for the title," Rooney, who now plays for Major League Soccer side DC United, told talkSPORT.
"I hope Man City get over the line before Liverpool. I couldn't bear to see them win it, it would be a nightmare for any Evertonian.
"I remember in 2005 (Liverpool) won the Champions League and they're still talking about it now so it would be another 10 or 15 years of that."