Andy Murray sealed Great Britain's place in the quarter finals of the Davis Cup with a pulsating win against Japan's Kei Nishikori (7-5 7-6 (8-6) 3-6 4-6 6-3) at the Barclaycard Arena in Birmingham. The 28-year-old Scot maintained his unblemished record in the tie to beat the world number six in five hard-fought sets of tennis to ensure his country's progression.

Prior to the tie, Murray had not played any competitive tennis since the Australian Open final in January, but he reserved his best performance of the week for his most difficult-looking assignment, narrowly overcoming the challenge of the Japanese number one.

The grand slam-winning star won a closely contested first set 7-5, and he took an eye-catching second - which featured some sensational tennis from both men - on a dramatic tie break (8-6).

At that stage, victory appeared an inevitability for Murray and Great Britain. But Nishikori dragged his country back into the tie by taking the third set 6-3, as Murray appeared to tire. And the Japanese player followed that up by winning the fourth 6-4, thereby setting up a dramatic finish to the most anticipated match of the tie.

What followed was a topsy-turvy, emotion-filled set, in which control of the match appeared to change in the space of a few shots. Ultimately, though, it was the Scot whose will and skill won out, as he held his nerve to serve for the tie after nearly five hours of play.

Murray subsequently admitted he struggled with his fitness levels during the match before finally overcoming Nishikori's stern challenge. "Physically I struggled a little bit at the end of the third set and a little bit throughout the fourth in the long rallies. I was struggling, he was pushing me quite far off the baseline," Murray explained during his post-match interview.

"I was trying to keep the points short, but you know, in the fifth set I just gritted my teeth, fought as hard as I can, gave everything and I managed to get the win."

He added: "Thankfully I managed to get through. I don't think we'll be playing the dead rubber today, I think everybody has seen enough tennis. We can go home and rest."

Victory in Birmingham means defending Davis Cup champions Great Britain now go into the quarter final of the competition, where they will face either Serbia - led by world number one Novak Djokovic - or Kazakhstan.