Former world number four Kei Nishikori's return to the ATP Tour after a lengthy injury absence ended in a first round 6-3, 6-4 loss to Sebastian Ofner.

Japan's Nishikori has barely played on the tour in the past two years with his last appearance on the ATP Tour coming at Atlanta July.

Given a wildcard by organizers, the 2016 Miami finalist was not surprisingly a little off the pace against 40th-ranked Austrian Ofner as he struggled to replicate his practice form.

"I thought I was practicing well, playing much better. I was feeling the rhythm and I was feeling the ball pretty good in the practice but during the match it's completely different," he told reporters.

"It was windy, he was hitting the ball very hard, very quick, the courts are quick. I was having a tough time making a lot of balls in the court and just the little things that I was not making, maybe I was supposed to hit the corner but the ball goes to the middle sometimes," he added.

At 34, Nishikori faces a real challenge to work his way back up the rankings but he believes that in time, he can get back to an elite level.

"I don't have the clear goal right now, you know I just want to play a lot of matches. I need some time to get used to (matches) and hopefully I can stay healthy, I think that's the only goal this year, I try to play as many matches as I can play," he said.

Gael Monfils, the 37-year-old Frenchman, turned on the style in his 7-6 (7/5) 6-4 win over Serbian Dusan Lajovic.

"It was a great match, he played well and I am still playing for these moments, these challenges. I feel like the fire is still there," he said.

Britain's Dan Evans battled back for a 1-6, 6-3, 6-4 win over Italian Lorenzo Sonego.

- Rybakina rallies -

In the WTA event, Caroline Wozniacki was a point away from winning in straight sets against Anhelina Kalinina but the Ukrainian ended up winning 5-7, 7-5, 6-4.

Wozniacki, who returned to the tour last year after a three-year absence, during which she gave birth to two children, reached the quarter-finals at Indian Wells last week.

Fourth-seed Elena Rybakina suffered a scare against Denmark's Clara Tauson before battling back for a 3-6, 7-5, 6-4 win.

Rybakina, who had wins in Brisbane and Abu Dhabi as well as a runner-up finish in Doha, had to miss Indian Wells due to illness and said she was still finding her way back to her best.

"I am happy with the win. It means a lot, I hadn't really played for more than a week and it's going to take time for me to get back in my best form but happy to get another chance," said Rybakina.

Maria Sakkari of Greece, beaten finalist to Iga Swiatek in California, defeated Yuan Yue 6-2, 6-2 to reach the third round.

Sakkari had lost her opening match in Miami in each of the last two years but she overcame the in-form Yuan, in one hour and 19 minutes.

The Chinese 25-year-old came into Miami after winning her first WTA singles title in Austin and then reaching her maiden WTA 1000 quarterfinal at Indian Wells.

Ninth seed Jelena Ostapenko, the 2017 French Open champion had to work hard for a 7-6 (7/3), 6-4 over qualifier Laura Siegemund of Germany.

Victoria Azarenka, a three time Miami Open winner, had to deal with some stong resistance from American Peyton Stearns before emerging with a 7-5, 3-6, 6-4 win.

Belarusian Azarenka won in Miami in 2009, 2011 and 2016.