Muliaina was granted extended leave at the end of the 2009 international season, and sat out the first three rounds this year while the Chiefs made an unbeaten start in South Africa and Australia.
He will return at fullback as the Chiefs open the fourth round at home to the Queensland Reds while winger Sivivatu has recovered more quickly than expected from a shoulder injury and will bolster the backline.
The Waikato forward pack remains depleted by injuries to locks Kevin O'Neill and Craig Clarke, No. 8 Sione Lauaki and prop James McGougan.
Waikato won its first three matches on the road and with the Bulls and Wellington Hurricanes are the only unbeaten teams after three rounds. The Bulls lead the tournament with 15 points while the Chiefs and Hurricanes each have 14.
Waikato, in its first home match of the season, and Wellington, who face the Cheetahs in South Africa, have the chance to take the outright lead in the absence of the Bulls, who have a fourth-round bye.
Muliaina said he was glad to be returning to an unbeaten team.
“It would have been hard watching them if they went the other way. To go away to South Africa and pick up 14 points out of 15 - we've never done that before - is something special,” he said.
Queensland's serious injury concerns were compounded this week by the loss of Wallabies winger Digby Ioane to a knee injury. The absence of fullback Peter Hynes with a finger injury and winger Rod Davies with a damaged cheekbone means the Reds will go into the match at Hamilton with a completely changed back three.
Wellington will also have a heavy injury toll to overcome when it takes on the Cheetahs in Bloemfontein on Saturday.
All Blacks Jason Eaton, Conrad Smith and Tamati Ellison were unable to travel with the Hurricanes because of injuries. Lock Eaton has been lost for the season with a knee injury while center Smith and utility back Ellison have less serious injuries and may rejoin the team for later matches in South Africa.
South African sevens player Robert Ebersohn will make his debut at center for the Cheetahs who have made four changes to the team which lost 31-24 to the Otago Highlanders in round three.
Coach Naka Drotske has named Hennie Daniller at fullback, Sarel Pretorius at halfback, Walti Vermeulen at lock and has moved Lionel Mapoe from center to wing to accommodate Ebersohn.
“I'm very confident now, especially after the disappointment of missing last week's game (with injury),” Ebersohn said.
“I'm looking forward to facing the likes of Ma'a Nonu who's an All Black and a world-class center. He's bigger than me, but I'm sure I'll be able to cope at this level.” The ACT Brumbies, 2-1 after three rounds, have named an unchanged lineup for Friday's match against the Lions at Canberra, their first home match of the season.
“We're very fortunate to be able to include the same 22 players for a third consecutive week,” coach Andy Friend said.
“While you definitely need that luck and consistency for a successful campaign, names on a page alone aren't enough to win you a championship.” In contrast, Lions coach Dick Muir has made eight changes to his starting 15 after last week's 33-18 loss to the Hurricanes, the most noteworthy the dropping of former All Blacks flyhalf Carlos Spencer to the reserves. Burton Francis was named at No. 10.
“We were bitterly disappointed at the result last weekend,” Muir said. “We were better than that.” The Lions also lost center Deon van Rensburg to a thumb injury but lock Willem Stolz returns from suspension as the team seeks its first victory.
All Blacks prop Tony Woodcock will return to the Auckland Blues front row for their important clash with the Canterbury Crusaders on Saturday. New Zealand captain Richie McCaw, who made his first Super 14 appearance of the season from the bench last week, was named on Thursday in the Crusaders' starting 15.
Auckland and Canterbury have 2-1 records.
“Both teams have good backlines, but it's really going to come down to the battle up front,” Auckland coach Pat Lam said.
“It's no secret the setpieces are crucial, lineout and scrummaging, and the quality of the ball will determine who will play the better rugby.” In other fourth-round matches, the New South Wales Waratahs meet the Sharks and the Stormers play the Highlanders.
Also without a win in the competition, the Sharks will give England flyhalf Andy Goode his first start in Saturday's match in Sydney.
Under pressure coach John Plumtree moved South Africa utility back Ruan Pienaar to scrumhalf and named Riaan Swanepoel at No. 12 in a reshuffled backline. Captain John Smit is returned to hooker, with Deon Carstens and Jannie du Plessis completing an all-Springboks front row.
Wallabies lock Dean Mumm is back in the New South Wales lineup after a two-week suspension. NSW suffered consecutive losses on its South Africa tour but coach Chris Hickey is determined the team will recover.
“We've learned some valuable lessons,” Hickey said.
The Stormers have been boosted by the return to fitness of captain and flanker Schalk Burger for the game against Otago in Cape Town on Saturday.
Highlanders coach Glenn Moore named an unchanged team on Thursday for the clash, keeping faith with the lineup that clinched Otago's first win of the season against the Cheetahs last weekend.
The other winless team, the Western Force, join the Bulls with a bye.