Tonga's quest for a first win in this year's IRB Pacific Nations Cup will face its toughest challenge yet with the visit of the Junior All Blacks to the Teufaiva Stadium in Nuku'alofa on Saturday.

The Junior All Blacks are not only the defending champions, but also the pacesetters in the tournament having picked up maximum points in beating Samoa 31-10 and Fiji 57-8 in the opening two rounds.

Their tour of the Pacific Islands comes to conclusion against Tonga, a team beaten 60-15 by Australia A in the opening round and then narrowly 20-17 by Japan last weekend in an encounter between the only two teams without a win in 2007.

Tonga head coach Quddus Fielea has made a number of changes from that defeat to Japan, some of them positional with Hale T Pole switching from flanker to number 8 with Teu'imuli Kaufusi coming into the starting line up.

Seti Kiole and 'Aisea Havili Kaufusi switch wings in a side captained again by flanker Nili Latu, while prop Soane Tonga'uiha, second row 'Isileli Fine, scrum half Soane Havea and full back Vungakoto Lilo given the nod to start in Fielea's other changes.

Tonga may have home advantage this time, having lost 38-10 to the Junior All Blacks in New Plymouth last year, but the defending champions will be looking to continue their impressive start to the Pacific Nations Cup that has so far yielded 13 tries in two matches.

The Junior All Blacks have made eight changes to the starting line up from the side that overpowered Fiji in Suva last weekend, one of them positional with Stephen Brett moving from inside centre to his more familiar role at fly half.

Jimmy Cowan will partner Brett at halfback with Sam Tuitupou filling the vacant centre spot, while in the only other backline change wing Scott Hamilton comes in for Rico Gear, who has three tries to his name this year.

In the front row props Clarke Dermody and John Afoa get the nod, while second row Tom Donnelly and flankers Kieran Read and Marty Holah also come in. Holah resumes the captaincy from co-skipper Daniel Braid, who drops to the bench.

"It is important that we build on our good start to the competition and we will certainly look to continue that in Nuku'alofa," co-coach Ian Foster said. "Saturday's game will be our third on consecutive weekends and we are mindful that we need to manage our players, hence the changes."

Familiar venue for Japan

The only other Pacific Nations Cup match this weekend sees Australia A host Japan at the Dairy Farmers Stadium in Townsville, a venue the Japanese will be familiar with after facing Scotland, France and Fiji there at Rugby World Cup 2003.

Australia A lie second in the standings with nine points, one fewer than the Junior All Blacks after failing to pick up a bonus point in last weekend's 27-15 defeat of Samoa, a margin made more comfortable with teenager Kurtley Beale's late try.

Coach Laurie Fisher has been forced to make changes to his Australia A team with scrum half Sam Cordingley called up to the Wallaby squad for their Test with Fiji and wing Lachlan Turner ruled out with a shoulder injury suffered early on against Samoa.

Josh Holmes, the IRB Under 19 Player of the Year, will start his first A game since June 2006 at scrum half, while Haig Sare replaces Turner and another will change see prop Gareth Hardy will make his Australia A debut.

The other changes made by Fisher see Will Caldwell and Dean Mumm step up from the bench into the second and back rows respectively, the latter forming a new flanker pairing with the recalled David Pocock.

Leading point scorer

Josh Valentine will provide cover for Holmes on the bench having been called up to replace the departed Cordingley, while prop Salesi Ma'afu is another newcomer named among the replacements by Fisher.

"The A programme is about giving guys an opportunity at this level and we're confident the mix of experience and new players will serve us well against Japan," admitted Fisher, whose side have the leading point scorer so far in wing Clinton Schifcofske with 35.

Japan though will arrive in Townsville buoyed by their victory over Tonga in Coffs Harbour - their first ever win in Pacific Nations Cup history after five previous defeats - and coach John Kirwan is looking for more improvement from his players.

"This is the level that we need to test ourselves and we need to know what we have got to work on to improve. For the Australia A match, I expect players to keep getting better. The victory last week was good, but I feel we can still improve," insisted Kirwan.

"We are not really worried about the opposition, we are still working on our process, what we need to do ourselves to be competitive … I think if we can achieve the things that we want, the game should go well.

Growing in confidence

"I see the improvements in our game plan … I think the defence is improving, but we still need to keep improving these things. Now that confidence is growing, we can now compete at this level."

Kirwan has made wholesale changes from that historic victory with only try scorer Kosuke Endo, Bryce Robins and Hare Makiri retained in the starting line up, although Robins moves from centre to fullback and Makiri from flanker to number 8.

Takamichi Sasaki steps up from the bench against Tonga to captain a side which features 10 players with 13 or less caps, including Kousei Ono, who only turned 20 in April but will win his second cap at fly half in a youthful halfback partnership with Yuki Yatomi.

The other match scheduled for round three was Fiji's visit to Apia to face Samoa, one that was brought forward to 19 May due to existing Test commitments this weekend. Samoa won 8-3 at a rain-soaked Apia Park for their only win to date.

Squads for IRB Pacific Nations Cup round three:

TONGA: 1. Toma Toke 2. 'Aleki Lutui 3. Soane Tonga'uiha 4. Sione Kalamafoni 5. 'Isileli Fine 6. Teu'imuili Kaufusi 7. 'Otenili Latu (Captain) 8. Hale T Pole 9. Soane Havea 10. Fangatapu 'Apikotoa 11. 'Aisea H Kaufusi 12. 'Isileli Matakaiongo Tupou 13. Hudson Tonga'uiha 14. Seti Kiole 15. Vungakoto Lilo.

Replacements: 16. Feki Moala 17. Sateki Mata'u 18. Lopeti Liku 19. Chris Hala'ufia 20. Tevita Palu 21. Siua Taumalolo 22. Sione Fonua.

JUNIOR ALL BLACKS: 1. Clarke Dermody 2. Derren Witcombe 3. John Afoa 4. Ross Filipo 5. Tom Donnelly 6. Kieran Read 7. Marty Holah (Captain) 8. Mose Tuiali'i 9. Jimmy Cowan 10. Stephen Brett 11. Anthony Tuitavake 12. Sam Tuitupou 13. Casey Laulala 14. Scott Hamilton 15. Cory Jane

Replacements: 16. Tone Kopelani 17. Wyatt Crockett 18. Jerome Kaino 19. Daniel Braid 20. Andrew Ellis 21. Stephen Donald 22. Tane Tu'ipulotu.

AUSTRALIA A: 1. Gareth Hardy 2. Tatafu Polota-Nau 3. Troy Takiari 4. Alister Campbell (Captain) 5. Will Caldwell 6. Dean Mumm 7. David Pocock 8. Jone Tawake 9. Josh Holmes 10. Berrick Barnes 11. Haig Sare 12. Ryan Cross 13. Junior Pelesasa 14. Clinton Schifcofske 15. Peter Hewat.

Replacements: 16. Sean Hardman 17. Salesi Ma'afu 18. Adam Wallace-Harrison 19. Julian Salvi 20. Josh Valentine 21. Gene Fairbanks 22. Kurtley Beale.

JAPAN: 1. Masahito Yamamoto 2. Mitsugu Yamamoto 3. Ryo Yamamura 3. Takanori Kumagae 5. Tsyuoshi Sato 6. Hajime Kiso 7. Takamichi Sasaki (Captain) 8. Hare Makiri 9. Yuki Yatomi 10. Kousei Ono 11. Hirotoki Onozawa 12. Koji Taira 13. Yuta Imamura 14. Kosuke Endo 15. Bryce Robins.

Replacements: 16. Yusuke Aoki 17. Tomokazu Soma 18. Hitoshi Ono 19. Glen Marsh 20. Koichi Ohigashi 21. Shotaro Onishi 22. Go Aruga.