It’s one of the most storied rivalries in men’s tennis but all won’t be as it seems when Novak Djokovic takes on Rafael Nadal in the ATP Cup decider on Sunday night.

Serbia and Spain make worthy finalists for the inaugural teams competition and the world No.1 and No.2 may well be clashing for the first and only time in the harbour city.

Ostensibly the pair are hard to split, with Djokovic holding a 28-26 career record against the Spaniard.

But on hard courts the fissure between them becomes an almighty crack.

Nadal hasn’t beaten Djokovic on the faster surface in almost six-and-a-half years, the Serb also winning nine of their last 12 encounters overall.

After a straightforward enough start to the tournament, Nadal has looked very human in the quarter and semi-finals, losing to David Goffin and on the cusp of getting beaten by Alex de Minaur.

Nadal largely deflected a question about his hard-court record against Djokovic but admitted he’d have to lift.

“I think I finished with positive energy (on Saturday),” Nadal said.

I know I have to be ready to play at my highest level to have my chance. I need something else, and I’m looking for it.”

Enjoying a 5-0 singles run at the ATP Cup, 16-time grand slam champion Djokovic has looked in the kind of form that could net him a record eighth Australian Open title.

It hasn’t all been straightforward. He was pushed to a third set tiebreak by Canadian Denis Shapovalov and Russian Daniil Medvedev also took him to three sets in a high-quality semi-final.

The 16-time grand slam champion said he was taking a lot of energy from his matches in Sydney.

“It’s the beginning of the season, and I’m not the only player that feels and talks this way, but I’m very motivated. I’m inspired to play my best tennis,” he said.

Novak Djokovic will hold the key to Serbia’s chances in the ATP Cup final. Photo: AAP

“For different reasons the conditions (in Australia) are suitable to my style of the game, and Melbourne Park, especially.”

The second singles match of the tie will pit Spain’s Roberto Bautista Agut against Dusan Lajovic.

Bautista Agut has been one of the standouts of the ATP Cup, the world No.10 demolishing Nick Kyrgios in the semi-final as part of a 5-0, ten consecutive set singles run.

A Wimbledon semi-finalist in 2019, he is 3-0 in career meetings with Lajovic who is 4-1 in singles for the tournament.

Doubles selection will likely come down to how the tie plays out, perhaps the ultimate result seeing the singles split so Nadal and Djokovic face off one more time for the road in Sydney.

-AAP