Though he will be 39 in November and has played over 900 games for the Reds, Blackmore believes there is more in Giggs' tank.
"I don't think this season will be his last," Blackmore told the Manchester Evening News.
"Ryan will be 40 in 2013, and as we stand now, I don't see why he couldn't be still playing for United then. For all the reasons I have given why he can make an Olympic impact for Great Britain, I believe the same stands when you are assessing his future. His game time is less these days but he is still having an influence and I could also see him ending his career as a full-back.
"I have seen him play there occasionally for United and I think he has the brain and ability to do it and get even more years out of him.
"He's a good tackler. He played rugby league as a youngster so he doesn't mind a bit of physical contact. He knows what will be in opposition winger's heads when they face him in a one-on-one. He wouldn't be easy to get away from, I can assure you of that, because he's still quick off the mark."