Gray was one of the stand-out performers for Scotland during last season's disastrous RBS 6 Nations campaign, while he was also impressive on the summer tour to the southern hemisphere, which included a famous 9-6 win against Australia.
Former Gloucester coach Redpath is undertaking an overhaul at Sale, with Gray and former England internationalist Danny Cipriani the highest-profile arrivals.
Gray will join a pack of forwards that already includes prop Andrew Sheridan, Welsh No.8 Andy Powell and one-time England flanker Hendre Fourie.
However, after his latest big-name arrival was paraded at Edgeley Park ahead of the weekend's JP Morgan Asset Management Premiership Rugby 7s Series, Redpath warned Gray to get in shape – and fast – or face a spell on the sidelines.
"The big thing for our new guys is that they have to get their fitness up to scratch," said Redpath. "Everyone coming in will be subjected to a conditioning course.
"There will be no exceptions. I'm a great believer that if you are fit, you can cope with most things that are thrown at you.
"Anyone coming in will have to fight to ensure their head is right and they are fit. When you are fit the game is easier and you are mentally stronger. When you are not as fit you tend to pick up injuries as you are not sharp and you get caught off balance.
"Having a player of the calibre of Richie is only going to help us develop, but he still needs to prove himself.
"The key is to build on what Sale achieved last season. Buying into the Sale culture as quickly as possibly will help us speed the process."
Gray was handed extended leave this summer by Redpath following his exertions with Scotland down under, hence the former Glasgow Warrior being spared a Sale introduction at the Rugby 7s Series on Friday night.
But after getting his first taste of the atmosphere in the north-west, Gray cannot wait to get going in a Sale shirt.
"I've met all the boys; they are a really friendly bunch of guys – they've made it easier for me to settle in," said Gray. "They came up, introduced themselves and shook hands. We've had a good laugh and so I'm delighted to be down here.
"Pre-season training has been quite tough – really tough, actually. It's been a bit of a shock to the system, so at the moment I'm looking forward to the weekends. I found some muscles I didn't know I had before. There were a lot of down-and-ups and with my height it wasn't exactly the greatest thing, but I got through it. I was close to being sick, though.
"I would love to have a great impact here and be part of a winning team, because that's what it's all about.
"I am sure most of the fans will be at the new stadium and it will be great to see them there for the pre-season game against Leinster.
"This is my first appearance in front of the Sale fans. It's been great watching the 7s and the crowd is brilliant. I know I'm going to be very happy here and, hopefully, very successful as well."
*To buy tickets for the JP Morgan Asset Management Premiership Rugby 7s Series visit: www.jpmorgan7s.com or call 08448 472492