The Wellington Hurricanes, Auckland Blues, Otago Highlanders and last year's finalist the Waikato Chiefs all hope to end midseason slumps and regain prominent positions in tournament standings.
After seven rounds only the third-place Canterbury Crusaders of New Zealand's five franchises remain strongly in contention for the semifinals.
The Hurricanes have had four straight losses and face seven-time champions the Crusaders in the opening match of the eighth round, needing a win to remain in the top eight.
The Chiefs won their first three matches on the road but since have had three losses to drop to seventh ahead of Saturday's match against Otago.
The Highlanders took a step away from the bottom of the ladder when they beat the Lions in round seven but must win again to keep the playoffs within reach.
The Blues, ninth with a 3-3 record, take on the toughest assignment when they host South Africa's unbeaten Bulls on Saturday.
In other matches, the winless Western Force take on the second-place Stormers, the fourth-place New South Wales Waratahs meet the Cheetahs and the improving Sharks return home from a five-match road trip to face sixth-place Queensland.
All Blacks winger Hosea Gear returns to the Hurricanes starting lineup for Friday's match after being sidelined with a knee injury and fellow international Piri Weepu starts at halfback in place of Tyson Keats.
The Hurricanes have paid heavily in their last four matches for their high-risk style and a lack of discipline.
“We've got to look at ourselves. It's personal pride really,” captain Andrew Hore said. “We're starting to run out of chances.” Coach Colin Cooper said his players had to lift their performance, reducing the handling and tactical errors which had littered their last two games.
“We'll be looking for a lot more composure than what we had against the Sharks,” Cooper said.
The Bulls, 6-0, will attempt to post their first-ever win over Auckland at Eden Park and to improve their record of only four wins from 31 games in New Zealand.
A Bulls win would also equal the Crusaders' record of 13 consecutive victories in Super rugby matches.
Coach Frans Ludeke named an unchanged side for the match, including lock Victor Matfield who will surpass former Stormers flanker Corne Krige's record of 53 matches as captain.
The Blues have concentrated this week on strategies to defend against the Bulls' rolling mauls.
“They are very good there and I think in their attacking zone, 75 percent of their lineouts they use to maul,” All Blacks lock Anthony Boric said. “For us that means first we have to compete as best we can in the air and then work on the ground.” All Blacks center Richard Kahui said the Chiefs were determined to re-establish their playoff credentials in Saturday's match against the Highlanders.
“We've just got to keep believing in what we're doing,” he said. “We've shown glimpses of how good this team can be and I think everyone still believes we can win this championship.” Injuries have forced the Chiefs into a backline reshuffle.
Mike Delaney starts his first match of the season at flyhalf, with Stephen Donald shifted to center alongside Kahui. Dwayne Sweeney will wear the No. 11 jersey in the absence of Sitiveni Sivivatu.
The Highlanders, meanwhile, have lost prop and vice-captain Jamie Mackintosh for six weeks with a toe injury.
Flanker Chris Alcock will make his debut for the Waratahs Saturday in place of captain Phil Waugh who has a leg injury. Dean Mumm will captain the Waratahs in a Super 14 match for the first time.
Prop Al Baxter will make his 100th Super rugby appearance for New South Wales while 22-year-old winger Lachie Turner will become the youngest player to make 50 appearances for the state.
Opponents the Cheetahs, who have not won since a home victory over Wellington in week four, will again be without captain Juan Smith who has stayed at home to be with his ill father.
Fullback Stefan Terblanche will reach 100 games when the Sharks play the Reds in Durban, and flyhalf Andy Goode is expected to line-up for his first match on South African soil. Reports say England flyhalf Goode has been granted a South African work permit and will stay with the Sharks for the rest of the Super 14 season.
The Stormers, with Springboks scrumhalf Ricky Januarie back in the team, move outside South Africa for the first time this season to play the winless Force at Perth on Friday.
“No overseas match is ever easy, but I want to see composure this Friday,” Stormers coach Allister Coetzee said.
