The Highlanders duo were among six players stood down last week for breaching team protocols after police were called to a party at Ioane's house in Dunedin following their loss to the Hurricanes.
But Brown says Ioane and Tomkinson have shown enough during the week to warrant their spots in the team after going through some extra punishment in training.
"They're quality rugby players," Brown said. "They were disappointed with what happened last week but that's in the past. They're going to go out and play good rugby on Saturday night and prove to everyone else that they're meant to be there."
"They got punished mate. Don't worry about that," Brown added when asked whether the players were up to the challenge.
"They just had to do a bit of extra fitness. Most of the guys who don't make the 23 have to work pretty hard to keep their fitness standards high so they were the same."
There were several other changes to the Highlanders squad, with Brown opting to rotate Siate Toklahi and Billy Harmon for Josh Hohneck and James Lentjes.
Scott Gregory moves from the wing to partner Tomkinson in midfield, with Thomas Umaga-Jensen out for the season, while Ngatugnane Punivai returns from a hamstring issue to start on the right wing.
Aaron Smith also returns to start in his familiar No 9 jersey after coming off the bench last week for Folau Fakatava, who suffered a season-ending ACL injury during his inspired performance against the Crusaders.
Brown said he was proud of how the leaders in the team stepped up last week to guide the side to an unlikely victory over the defending champs and hopes for a repeat performance against a tricky Chiefs side.
"I just think the leadership was really good during the week. Yes we had some conflict, which created a bit of an edge within our environment but the leaders took over the team and led the team well. And then the younger players just played rugby.
"I think if we can back up last week's win with another quality performance then we're a shot at trying to make the final."
Meanwhile, Chiefs coach Clayton McMillan has called on loose forward Kaylum Boshier to fill the hole left by injured captain Sam Cane for this weekend's clash.
He beats out older brother Lachlan who misses out on the 23 entirely.
"[Lachlan's] good to go but just felt this week under the roof down in Dunedin, it would've been a tough ask to go out there without any minutes under his belt since 30 in pre-season," McMillan said.
"He's been sent off to play club rugby and hopefully that'll put him in good stead for next week."
McMillan said his selections, which also sees Pita Gus Sowakula miss out on a place in the starting squad, were based on positional cohesion.
"You get cohesion when people have played in the same position often, and ideal with the same people.
"Over the last couple of weeks we've managed to achieve that to a large extent."
All Blacks lock Tupou Vaa'i is back in the starting side, returning from concussion in place of Samipeni Finau.
Etene Nanai-Seturo and Jonah Lowe both take their places on the left and right edges, replacing Sean Wainui and Shaun Stevenson.
Highlanders: 15. Connor Garden-Bachop, 14. Ngatungane Punivai, 13. Patelesio Tomkinson, 12. Scott Gregory, 11. Jona Nareki, 10. Mitch Hunt, 9. Aaron Smith (cc), 8. Kazuki Himeno, 7. James Lentjes, 6. Shannon Frizell, 5. Pari Pari Parkinson, 4. Bryn Evans, 3. Josh Hohneck, 2. Ash Dixon (cc), 1. Ethan de Groot.
Reserves: 16. Liam Coltman 17. Ayden Johnstone 18. Siate Tokolahi 19. Josh Dickson 20. Billy Harmon 21. Kayne Hammington 22. Josh Ioane 23. Hugh Renton
Chiefs: 15. Damian McKenzie, 14. Jonah Lowe, 13. Anton Lienert-Brown, 12. Quinn Tupaea, 11. Etene Nanai-Seturo, 10. Kaleb Trask, 9. Brad Weber (c), 8. Luke Jacobson, 7. Kaylum Boshier, 6. Mitchell Brown, 5. Naitoa Ah Kuoi, 4. Tupou Vaa'i, 3. Angus Ta'avao, 2. Samisoni Taukei'aho, 1. Aidan Ross
Reserves: 16. Bradley Slater, 17. Ollie Norris, 18. Joe Apikotoa, 19. Samipeni Finau, 20. Pita Gus Sowakula, 21. Te Toiroa Tahuriorangi, 22. Alex Nankivell, 23. Shaun Stevenson
