2016 my 'most successful' season: Nishikori

World number five Kei Nishikori has referred the 2016 as his most successful tennis season results-wise, before adding that he is targeting a Grand Slam title next year.

"Result-wise this has been my best year. I've played well against the top-10 players and have been winning against the likes of (Rafa) Nadal and (Andy) Murray, who I couldn't beat before. I'm making fewer mistakes as I get older. I hope to keep building, bit-by-bit," Sport24 quoted Nishikori as saying.

Although the 2014 US Open runner-up insisted of having a successful year, he admitted that he needs to win some big tournaments.

"A year that I won most matches does carry some significance but what is important is how much I can win at big tournaments," Nishikori said.

The 26-year-old also believes he holds the ability to challenge the world's top tennis stars.

"I'm confident I have the ability to challenge for world number three and four. I need to be more cautious while determining which points in the match I have to focus and how I can win break points in a more assured manner," the Japanese player said.

Nishikori concluded the season as the World No. 5 with 58 wins to his name, including one ATP title and an Olympic medal at the Rio Games.

In the grand slams, Nishikori reached the Australian Open quarter-finals, fourth rounds of the French Open and Wimbledon before making it to the semi-finals of the US Open, where he lost to tournament winner Stan Wawrinka.

Nishikori also made it to the last four of the ATP World Tour Finals in London and reached to the finals of the ATP Swiss Indoors, ATP Rogers Cup and the ATP Miami Open.