Gatland had manage to make Peter O’Mahony his captain in the first test and then dropped him straight out of his match day squad in one week.
That now gives Wales Sam Warburton the captain armband for the British & Irish Lions second test against New Zealand in Wellington on Saturday.
Gatland also picked Sexton at 10 moving England’s Farrell to inside centre and up front he brings in Itoje for Kruis.
He made changes on the bench as well with Courtney Lawes, Jack Nowell and CJ Stander all coming into the squad after he thought they impressed against a second string Hurricanes side.
Gatland said: “We saw Maro’s impact in the first Test and he will bring an edge and a physicality, as will Sam Warburton in terms of pressure on the ball.
“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 first Test and there were a few that we didn’t finish.
“There were lots of positives from the first 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: 15 Liam Williams, 14 Anthony Watson, 13 Jonathan Davies, 12 Owen Farrell, 11 Elliot Daly, 10 Johnny Sexton, 9 Conor Murray, 8 Taulupe Faletau, 7 Sean O’Brien, 6 Sam Warburton (c), 5 Alun Wyn Jones, 4 Maro Itoje, 3 Tadhg Furlong, 2 Jamie George, 1 Mako Vunipola
Replacements: 16 Ken Owens, 17 Jack McGrath, 18 Kyle Sinckler, 19 Courtney Lawes, 20 CJ Stander, 21 Rhys Webb, 22 Ben Te’o, 23 Jack Nowell