Andy Murray revealed he played through the pain barrier to help seal Great Britain`s first appearance in a Davis Cup final since 1978.
The world number three handed his side an unassailable 3-1 lead in their World Group semi-final clash against Australia following his 7-5, 6-3, 6-2 victory over Bernard Tomic in the first reverse singles rubber on Sunday.
Britain`s Dan Evans lost 7-5 6-4 to Thanasi Kokkinakis in the final rubber.
Britain will now face an away trip to take on Belgium in the final, due to played between November 27-29, after they defeated Argentina 3-2 in the second semi-final tie.
Murray won both singles` matches and the doubles with brother Jamie as he played on three successive days to secure a first victory over old rivals Australia since 1978.
But the 28-year-old revealed that a back injury sustained in training last Tuesday had been a cause for concern throughout the tie.
"My back had been giving me a lot of trouble this weekend and for a few days before the tie as well," Murray said.
"The previous issues I`ve had with my back have been completely different. My back was fine during the US Open and all through that stretch.
"I took five days off and started practising again. On Tuesday night, once I had finished practising and had cooled down, my back was extremely sore and it got progressively worse over the next couple of days.
"I didn`t feel it when I was playing on the Tuesday so I don`t know exactly what happened.
"Sometimes after you have played a lot of tennis and then you do take a break the muscles and everything stiffen up and you can have some issues."It puts nine-times winners Britain, on the verge of relegation to Zone Group III five years ago, a step closer to an historic first title triumph since 1936.
Murray is now looking to become only the fourth player ever to win the Davis Cup, Olympic gold and multiple Grand Slams.
"Obviously I`m delighted to get through. We knew this would be difficult, Australia have so much depth and experience but we fought extremely hard all weekend," the world number three said.
"It has been a very tough weekend for me physically; and mentally it`s so draining as well.
"We have an opportunity to win the event in the next match but there`s so much tennis still to go.
"We still need to win three matches and there`s two or three months until the next tie and a lot can happen between now and then.
"Belgium have a player in David Goffin who is very close to being in the top ten in the world and they will be playing at home on whatever surface they choose, but it will be the one they think will give them the best chance.
"So there`s no guarantees, but reaching the final is a big achievement in itself. It hasn`t been done in a long time and everyone in the team can be very proud of that.
"It would be an incredible achievement to win it but there`s a long way to go."
It was a final Davis Cup campaign for Australian veteran Lleyton Hewitt, who is set to retire following the Australian Open in January 2016.
"It is a great honour. I have never shied away from it," Hewitt, tipped as the next Australian Davis Cup captain, said of representing his country.
"Tennis is a very selfish sport and I have always loved getting together as a group and playing for your country.
"We did everything we could have done in this tie. We laid it on the line again so I`ve no regrets, but at the same time I`m disappointed as we were so close to having the opportunity to play in another Davis Cup final.
"I`ve been lucky and had the opportunity to celebrate at the end of a winning campaign like 2003 and my first year in 1999, but I`ve definitely had my fair share of gut-wrenching losses as well.
"These boys are going to get a lot more opportunities and they will be better players because of what happened this weekend."