PERTH:World number one Rafael Nadal overcame sluggish serving to start his season with a 6-3, 7-5 victory over Nikoloz Basilashvili on the second day of the inaugural ATP Cup on Saturday.

The 19-time Grand Slam winner clinched the tie for Group B favourite Spain against Georgia after world number nine Roberto Bautista Agut downed unheralded Aleksandre Metreveli 6-0, 6-0 in 71 minutes.

Nadal was made to work in the contest lasting one hour and 49 minutes, his first of the season as he eyes equalling Roger Federer's record Grand Slam tally -- of 20 titles -- at the Australian Open late this month.

"It was a tough first match-up of the season. It was not an easy start," Nadal said. "I had some mistakes but was able to close it out."

It was his first match since he spearheaded Spain's Davis Cup title on home soil alongside Bautista Agut in November.

Thiem confident 'Big Three' will be toppled at Slams

"We had great experiences playing on the team and representing our country and here we are again. We want to try our best," he said.

Nadal started slowly against Basilashvili and was broken in the opening game to quieten the near capacity crowd in his first-ever match in Perth.

But he bounced back immediately and gained the break with a sizzling winner down the line.

World number 26 Basilashvili, who had been soundly beaten by Nadal twice previously, was undaunted and impressively countered on the baseline to stay in the contest.

Nadal, however, made his move with a break in the eighth game to gain control and draw first blood shortly after.

His momentum continued as he stormed out to a 5-2 lead in the second set but was unable to serve it out twice before eventually overcoming Basilashvili's spirited challenge

In the earlier match, Bautista Agut expectedly crushed world number 679 Metreveli, who was playing his first match on the ATP Tour.

Metreveli, 26, started enterprisingly and had a golden opportunity to get on the board early but lost a marathon 15-minute second game on serve. It was one way traffic from there as Bautista Agut took command with pinpoint groundstrokes to rattle his inconsistent opponent.

Nadal aims to carry momentum into 2020

"I asked players who knew him for information because I had never seen him play," Bautista Agut said. "I was focusing on my game and I played a great match."

Japan also started strongly after sweeping Uruguay in the earlier Group B tie. World number 73 Yoshihito Nishioka thrashed higher-ranked Pablo Cuevas with a 6-0, 6-1 rout in just 54 minutes.

Nishioka put on a masterclass over a dispirited Cuevas, but was helped by his lacklustre opponent who did not hit a winner during a grim first set.

The left-handed Nishioka caused the world number 45 problems and clinched the tie after Go Soeda put Japan ahead with a comfortable 6-1, 6-3 victory over Martin Cuevas, Pablo's younger brother.

Soeda had replaced world number 13 Kei Nishikori, who withdrew from the tournament and the Australian Open with an elbow injury.