Serbia had to win both the reverse singles to make it to the quarterfinal after Kazakhstan had taken a 2-1 lead. Despite being an overwhelming favourite, Djokovic found the going tough against a determined Kukushkin who led the match two sets to one.
Djokovic dug deep and won the next two sets to level the score 2-2. The world number one hit 19 aces and 37 winners but committed 94 unforced errors in his win which Djokovic termed as one of the most difficult matches in his career both physically and mentally.
Serbia will now face Great Britain in the quarterfinals after the defending champions beat Japan 3-1. The tie witnessed yet another titanic battle, this time involving world no 2 Andy Murray.
Murray too clocked almost five hours in his epic five set win over Kei Nishikori in Birmingham. Murray’s win seemed to be just a formality after he won the first two sets. However, Nishikori stormed back in the match by taking the next two sets and was even a break up in the fifth. However, Murray raised his game to clinch the deciding set and the match.
Murray hit 10 aces and 40 winners but suffered 97 unforced errors in the gruelling encounter.
In the other matches, Argentina beat Poland 3-2, Italy whitewashed Switzerland 5-0 and Croatia defeated Belgium 3-2.