Novak Djokovic spearheads Serbia's bid to reach the Davis Cup semi-finals for the first time since 2013 and reboot a career which has stalled since his history-making French Open victory.
Although Djokovic is still number two in the world the 29-year-old remains a shadow of the man whose maiden Roland Garros title in June last year allowed him to boast ownership of all four majors.
Shock early losses at Wimbledon, the Rio Olympics and Australian Open have been compounded by a recent elbow injury which sidelined him from the Miami Masters.
Since the start of 2017 Djokovic has won just seven matches but he insists that this weekend's Davis Cup clash at home to Spain provides the perfect platform for the defence of his French Open title, the only Grand Slam still in his possession.
"I always draw very positive energy from these weeks," said Djokovic, who won the Davis Cup in 2010, as he sat alongside teammates in Belgrade where the quarter-final takes place.
"I have shared some amazing moments in my career, in my life, with the people that are sitting at this table.
"Playing for our country in the official team competition -– the only official team competition we have in (this) sport -– is definitely very special," added Djokovic, who is on an 11-match win streak in Davis Cup singles.
Five-time champions Spain won the only previous meeting between the two countries 4-1 in 2009, with Rafael Nadal defeating Djokovic in the decisive rubber.
But eight years on and Nadal has opted out of the trip to Belgrade, choosing to rest ahead of the imminent clay court season and his prime target -- a 10th French Open title.
World number 19 Pablo Carreno-Busta will instead lead Spain's assault on a first semi-final spot since 2012.
- 'Three Musketeers' missing -
The winners of the tie will take on either France or Great Britain for a spot in the final.
The European rivals meet on an indoor clay court at Rouen with Britain hampered by the loss of world number one Andy Murray, out with an elbow injury.
World number 44 Dan Evans is Britain's top-ranked singles player despite not having played on clay for three years, while 17-ranked Lucas Pouille shoulders French hopes with leading men Jo-Wilfried Tsonga and Gael Monfils not in contention.
Nine-time winners France have gambled by handing the second singles spot to veteran Jeremy Chardy despite the world number 68 not having played in the tournament for six years.
Chardy replaces Gilles Simon meaning it will be the first time since 2005 that France's self-styled "Three Musketeers" of Tsonga, Monfils and Simon have not been named in a Davis Cup line-up.
"It wasn't an easy choice but I think it was the better solution," said France captain Yannick Noah.
In Brisbane 28-time winners Australia host the United States, Davis Cup champions on a record 32 occasions.
The two countries meet for the 47th time in tournament history with firebrand 16th-ranked Nick Kyrgios, fresh from his epic three-set loss to Roger Federer in the Miami semi-finals, taking the role of Australia's top singles player.
With teammate Jordan Thompson, 79 in the world, Kyrgios be relied on to take both singles rubbers.
However, the US boast two top-25 players in Jack Sock and John Isner.
The winners of that tie will meet either 2015 runners-up Belgium or Italy, who stunned defending champions Argentina in the first round, for a final spot.
Italy's chances of seeing off Belgium in Charleroi were hit on Wednesday when Fabio Fognini, who came from two sets down to win the decisive rubber in Argentina in February, was ruled out with injury.
World number 122 Alessandro Giannessi replaces Fognini.