The 23-year-old has not played since Sale's Heineken Cup clash with Cardiff Blues on October 14 - one of two wins for the Sharks this season - but was named in Scotland head coach Andy Robinson's starting XV on Tuesday before passing a fitness test.
"I managed to get my ankle right so I'm fit and raring to go," Gray said.
"It's been a tough couple of weeks, just trying to get my ankle back to where I wanted it to be.
"Thankfully I got it right in time to face New Zealand; it's an opportunity that doesn't come around too often.
"It will be a pretty tough shift, but I'm looking forward to it."
Gray, who joined Sale from Glasgow Warriors in the summer, thanked the Aviva Premiership side for their support despite their torrid start to the season.
Having not played for a month is far from ideal preparation for a match with the world's best side.
His was not the only injury in the front five ahead of Scotland's first Test since June, when they claimed wins in Australia, Fiji and Samoa, but Gray claims the pack are fit and firing.
Gray, who was awarded his first Scotland Test start against the All Blacks two years ago, added: "There has been a few injuries, but we've certainly managed to do all of our drills and we're very confident going into the game. There's been a real energy around training."
Gray's second row partner Jim Hamilton has required treatment for a rib injury in the build-up, while Scotland's options at prop have dwindled due to a succession of injuries and the fact Euan Murray is unavailable as the match falls on a Sunday.
Geoff Cross is to start at tighthead, Murray's specialist position, with Ryan Grant, the starting loosehead, providing cover.
Gray added: "Ryan Grant's a quality player. He's been scrummaging at tighthead and it's went very well. All the boys have confidence that he'll do a job.
Gray is one of Scotland's most talented players and performs at a consistently high level and he knows everyone must perform at their very best to beat the world champions.
He said: "It will be very tough. It's about getting in their faces, putting them under a lot of pressure and, in defence, work rate, working really hard for each other and doing that for 80 minutes."
Two years ago four of New Zealand's tries came from turnover ball, after Scotland were stripped of possession.
"New Zealand are one of the best counter-attacking teams in the world, absolutely lethal," Gray added.
"We'll need to do our best to keep the ball. Mistakes do happen, but it's about us being sharp and getting into defence as quickly as possible."
In 28 previous meetings over 107 years, Scotland's best results against the All Blacks have been two draws.
If Scotland are to pull off an historic victory, the performance of Edinburgh half-back Greig Laidlaw will be key.
Laidlaw made his Scotland debut as a replacement scrum-half in the 49-3 defeat in 2010, but will start at fly-half on Sunday.
His opposite number could be one of the most celebrated players the game has ever seen in Dan Carter, with New Zealand to confirm their team tomorrow.
Laidlaw said: "I'll be looking forward to it if he (Carter) does play. He's a fantastic player and he has been ever since he's played for New Zealand."
Laidlaw is slight at 12st 8lb (80kg) and 5ft 9in (1.76m) and is used to his defensive channel being targeted.
New Zealand, with the likes of centre Ma'a Nonu, are sure to do so.
"I'm used to it by now," added the Edinburgh captain, who is looking forward to linking up again with scrum-half Mike Blair, now at Brive.
"It happens to me most weeks. I've worked a lot on my defensive qualities and I think that's shown through for Edinburgh this year."
As for the possibility of victory, Laidlaw added: "It would be outstanding. As a group that's our focus going into the weekend.
"If we were to do it, it would be the best victory for Scottish rugby ever, but it's going to be a hard task. There's no denying that.
"We respect New Zealand, they're a top team, but we need to concentrate on ourselves.
"If we worry about them we're beaten already. We need to go out there, do the things we've worked on in training and take it from there."
Gilbert has released a new line of rugby cleats. The Gilbert Virtuo 8S is part of the exciting new product. Check it out.
The entire All Blacks apparel line has been updated for 2013/14. Check out the New Zealand All Blacks polo.
The Nike Tiempo is a solid rugby cleat and one of few styles still made from full-grain natural leather.
The Gilbert Blitz 8S rugby cleat is a great cleat at a great price of $69.99. Get a new pair of cleats today.
A cool looking all black rugby cleat with the high performance adidas is known for. Get in the Gear!
Wear the crest of the British and Irish Lions on your t-shirt. A great look for the summer.
The All Blacks Performance t-shirt is black with hints of blue from the training jersey. Very Cool.
The New Zealand All Blacks training jersey for 2013/14. Get in the Gear!
The USA Rugby Pro Alternate rugby jersey is perfect for any fan of the Eagles. Get yours to wear during the summer Test matches.
The NEW All Blacks 2013/14 jersey has arrived at World Rugby Shop. Dare to wear the colors of the All Blacks.