Wayne Rooney scored his 250th goal for Manchester United on Saturday, surpassing the mark previously held by Sir Bobby Charlton.
Rooney has been with Old Trafford since 2004.
"When Wayne Rooney joined the club I could never imagine anybody could beat Sir Bobby's record," Sir Alex Ferguson told MUTV.
"So his achievement is outstanding. It's amazing. He's 200-odd games short of Bobby's playing record and that makes it even more amazing.
"I don't think anyone can [overtake Rooney]. I couldn't say never -- never say never -- but if you look at modern-day football, Manchester United are one of the few clubs who can keep players for over 10 years.
"It is more difficult than ever but we were very lucky if you look at my time, even in Sir Matt Busby's time, we had players who stayed for more than 10 years.
"Many, many players did that. But in the modern day, you see it happening less and less that players stay for that length of time.
"For instance, Jose [Mourinho] mentioned young Marcus Rashford and he's got to score more than 20 goals a season for the next 10 years or so [to beat Rooney's record] and that is difficult in itself."
Via PA Sport