Suntory Sungoliath booked themselves a spot in the playoffs to determine the Japan Rugby Top League champions on Saturday thanks to a 28-13 win over NEC Green Rockets.

The victory at Prince Chichibu Memorial Rugby Ground means Keisuke Sawaki's team cannot finish outside the top two in the Red Conference.

This season the league has been split into two conferences of eight teams.

Teams play the seven other sides in their conference plus six from the other group to determine the rankings for the end of season playoffs, with the top four sides competing for the league title, which doubles as the All-Japan Championship.

There are three other playoff blocks to determine fifth to 16th positions with the bottom side automatically relegated.

"The result was good enough to get into the playoffs but we did not perform at the level we need to play to win the finals," said Sawaki.

The 42-year-old former flyhalf was particularly upset with the way his side kept losing the ball at the breakdown.

"We kept making the same mistakes. Children can fix things if they repeatedly make the same mistakes but we couldn't today," he said.

Suntory head their group by nine points from Toyota Verblitz who beat NTT Docomo Red Hurricanes 46-18, with Kobe Kobelco Steelers a further two points back following their 39-22 victory over Kintetsu Liners.

Meanwhile in the White Conference, Panasonic Wild Knights, who take on Munakata Sanix Blues on Sunday, need just three points from their final three games to clinch top spot.

The Wild Knights have 49 points, eight more than Yamaha Jubilo, who beat Coca-Cola Red Sparks 54-7 on Saturday and 10 more than Ricoh following the Black Rams' 35-20 win over Toyota Industries Shuttles.

In the day's other game between two sides that look set to play off for either fifth to eighth place or ninth to 12th spot, NTT Communications Shining Arcs edged Canon Eagles 8-3.

The first game of the day at Chichibunomiya opened with Rui Shimizu very much the center of attention.

The referee first sent Suntory flanker Masakatsu Nishikawa to the sin bin in the third minute for a dangerous tackle, before showing NEC fullback Hiromasa Yoshihiro a yellow card for a deliberate knock-on six minutes later.

Yoshihiro's offence came five meters from the NEC line and Shimizu had no option but to award Suntory a penalty try for good measure.

NEC flyhalf Yosuke Morita closed the gap with a penalty that just managed to creep over the crossbar in the 20th minute.

But two penalties from Matt Giteau and a try from Yasunori Nagatomo, converted by Giteau from the touchline, made it 20-3 at the break.

"We were very ill disciplined in the first half," said NEC coach Peter Russell. "We had our chances but against a side like Suntory you need to convert pressure into points."

NEC opened the second half with a superb try from Maritino Nemani following good work from Morita and his halfback partner Tomonori Kimura.

Morita banged over the extras and then added a penalty in the 54th minute to make it a 20-13 game.

But with Suntory able to call off the bench the likes of Shinya Makabe and Yutaka Nagare -- who along with Shintaro Ishihara and Kotaro Matsushima are set to sign with the Sunwolves in the coming weeks -- it was the Sungoliath who finished strongest, despite an unusual number of handling errors.

Giteau kicked a third penalty in the 68th minute before Daishi Murata sealed the win with a try two minutes later.