The only outfield players to have appeared in the Barclays Premier League beyond 40 are Gordon Strachan and Teddy Sheringham, two former United men who reached the milestone with Coventry City and West Ham respectively.
Enlarge Life of Ryan: Giggs is keen to sign another one-year extension with United
Giggs does not celebrate his 40th birthday until November 2013, but Ferguson believes it is far from certain that this will be the 37-year-old's last new deal. 'I spoke to Ryan a few days ago and he's happy to have another year,' said Ferguson yesterday.
'He could do another year and who knows, another two years, because his fitness is incredible.
'I never expected him to be here so long, but as the years went on there were improvements in sports science and fitness, and Ryan is very much into yoga too. He's also been prepared to make sacrifices and be a really good professional.'
Eye on the ball: Giggs is playing in his 21st consecutive season for United
Giggs is the most decorated player in the history of English football and also holds the record for most appearances at United.
The former Wales player is used more sparingly by Ferguson these days but admitted he is looking forward to extending his Old Trafford career.
'I am quite happy still playing at the moment and enjoying my football as much as ever,' said Giggs. 'The manager would be the first one to tell me if I wasn't playing well, or my form wasn't good. We are a lot more honest with each other now. It's a great relationship and one that has been a big part of why I'm still playing.'
Special relationship: the Welshman admits he and Fergie are more honest with each other than they use to be
With rivals Manchester City not playing at Aston Villa until 5.30pm today, United hope to extend their lead at the top of the table against Birmingham beforehand.
Goalkeeper Ben Foster could face a mixed reception on his return to Old Trafford after speaking out on behalf of the Glazer family when he completed a £6million move to St Andrew's in the summer, telling rebel United fans 'to focus on just supporting the club a bit more'.
But one player who will be missing is Rafael da Silva, who was fined £8,000 by an FA disciplinary commission yesterday but escaped with just a one-game ban over his tirade at referee Mike Dean.
The United defender reacted furiously when Dean showed him a second yellow card at Tottenham last Sunday. Rafael, 20, admitted a charge of improper conduct.
I'll put Rafael in there, and they wouldn't know. Fergie will pretend it's his twin, Fabio Sunderland have got more chance of signing me than Welbeck, says Fergie All the latest Manchester United news, features and opinion
Explore more:People: Alex Ferguson, Gordon Strachan, Mike Dean, Ryan Giggs, Teddy Sheringham, Ben Foster Places: Birmingham, Wales