Rooney became the third-highest scorer in the club's history with his brace against West Ham United on Saturday and now sits just 25 goals behind Denis Law and 37 short of Sir Bobby Charlton.
Moyes was full of praise for the 28-year-old and backed him to go on and break both records before he calls time on his spell at Old Trafford.
"If you are third top scorer of a club like Manchester United you already are a legend. As long as he doesn't pick up any serious injuries he has a real good chance of breaking Denis Law's and Sir Bobby Charlton's [records] and that would be some feat," Moyes is quoted as saying by PA.
Rooney has netted 212 goals in 436 appearances for United.