Harrison has signed on for three more full seasons at the AJ Bell Stadium and Macleod will be remaining with the Sharks for two more years after extending his deal until 2016.
Sale boss Steve Diamond is convinced 21-year-old Harrison will represent England one day, while 30-year-old Macleod has been one of Sale's most consistent performers since joining from Cardiff Blues five years ago.
"We see a massive future for Ross. He has definitely got a full representative future with England ahead of him if he carries on in the way he's going," said Diamond, whose side sit top of Amlin Challenge Cup Pool 1 and are currently one place shy of a Heineken Cup spot in the Aviva Premiership.
"As far as Nick is concerned, he's a model professional who has been at the club for five years now. His kicking statistics are high and we are really glad that he has agreed to stay on for another two years with us."
As for Addison, having the academy product back in the ranks must almost feel like a new signing for Sale given that he hadn't played at all this season until a fortnight ago.
The 21-year-old Cumbrian had been struggling with a succession of injuries but finally found his way back to full fitness to start his side's last two competitive games. He was in fine form in both, as Sale saw off Harlequins in the LV= Cup before beating bottom-placed Worcester Warriors in the league last Friday.
Addison set up a try for veteran wing Mark Cueto with a superb cross kick in the win over Worcester and he believes he has come back better than ever as Sale look to build on a promising start to the season.
"I've put weight on and I'm in the best shape I've ever been and feeling fantastic on the pitch as a result," Addison told the Manchester Evening News.
"The conditioners and physios have done a great job with me and I've put on a couple of kilos this summer while still feeling as agile and powerful as I ever was and I'm definitely a lot heavier than when I started in the first team two-and-a-half years ago.
"While I was out injured, I was able to train on my own and focus on my own and I could do a couple of extra weight sessions a week and I think it's just a natural progression when you get older. It's about growing in the game and becoming a wiser player and hopefully that's showing in the way I both play and train at the moment."
Sale return to Amlin Challenge Cup action with a double header against French Top 14 newcomers Oyonnax a week today having got the better of 2012 tournament winners Biarritz Olympique on home soil in the opening round of action and then picked up maximum points at Worcester at week later.
Addison admits that coming back into the fold when things are going smoothly for Sale - particularly given how they started last season when they lost seven straight league games - has made life easier and even more enjoyable.
"It's been great to have come back into the team in the position we are and the way we are playing," continued Addison. "Our training levels are 10 times what they were last year and that's thanks to the new guys who have come in - they have upped the standards and the level of competition, which shows the quality we have got."