"It's tough on Peter O'Mahony who has done a brilliant job for us. We had to look at the bench and we felt that CJ Stander's ball carrying and defence was the right choice for the bench. You have to make the tough calls and pick what is the right team and the right combinations for a Test match."
Gatland added: "In terms of the backs we have gone with the Sexton-Farrell combination. Both have played well and it gives us that attacking option in the 10-12 channel. We created opportunities in the 1st Test and there were a few that we didn't finish.
"There were lots of positives from the 1st Test but we were disappointed that we put ourselves in a position to put the All Blacks under pressure and to get back into the game and we let it slip.
"This is a big chance for these players to go out and show what they are capable of on Saturday night. For the players retained from the first Test it's an opportunity for them to step up and to show an improvement because individually they were disappointed and you have another group coming in who are also desperate to seize their chance."
British & Irish Lions squad
15. Liam Williams - Scarlets, Wales
14. Anthony Watson - Bath Rugby, England
13. Jonathan Davies - Scarlets, Wales
12. Owen Farrell - Saracens, England
11. Elliot Daly - Wasps, England
10. Johnny Sexton - Leinster, Ireland
9. Conor Murray - Munster, Ireland
1. Mako Vunipola - Saracens, England
2. Jamie George - Saracens, England
3. Tadhg Furlong - Leinster, Ireland
4. Maro Itoje - Saracens, England
5. Alun Wyn Jones - Ospreys, Wales
6. Sam Warburton (capt) - Cardiff Blues, Wales
7. Sean O'Brien - Leinster, Ireland
8. Taulupe Faletau - Bath Rugby, Wales
Replacements:
16. Ken Owens - Scarlets, Wales
17. Jack McGrath - Leinster, Ireland
18. Kyle Sinckler - Harlequins, England
19. Courtney Lawes - Northampton Saints, England
20. CJ Stander - Munster, Ireland
21. Rhys Webb - Ospreys, Wales
22. Ben Te'o - Worcester Warriors, England
23. Jack Nowell - Exeter Chiefs, England