Winger Tommy Bowe will start on the wing in place of Alex Cuthbert after making a quick recovery from a broken hand, while scrumhalf Ben Youngs replaces Mike Phillips in the only changes to the backline that helped secure a 23-21 victory in Brisbane.
Gatland made two forced changes to his starting pack for the match at Docklands Stadium with Mako Vunipola at loosehead prop after Alex Corbisiero was ruled out with a calf injury and lock Geoff Parling coming in for the injured Paul O'Connell.
Loose forward Dan Lydiate replaces Tom Croft after leading the midweek side to a confidence-boosting 35-0 victory over the Melbourne Rebels on Tuesday.
"He's obviously quality. I think with Tommy it's the experience that he brings," Gatland said of bringing Bowe back into the side. "He's solid and really well this week."
Gatland said the abrasive Phillips had missed some training this week due to knee soreness after the match at Lang Park, but was fit.
"The decision was to rest him for this week, he's a potentially important component for next week," he added.
"Just given the quality of the nines we've got, I mean all of them have done a great job so far, and we felt it was prudent to make sure he was 100 per cent for next week."
Prop Ryan Grant, a late call-up for the tour, has come onto the bench as one of the front row replacements, while flanker Sean O'Brien and scrum-half Conor Murray have been brought into the matchday 23.
"We've decided to add a bit more physicality to our side up front and Dan brings that, and then we've got the explosiveness off the bench with Tom Croft and Sean O'Brien can give us that as well," Gatland added.
"It just shows how strong the squad is. It just shows that we've got a huge amount of competition in the team."
Lions: 15-Leigh Halfpenny (Wales), 14-Tommy Bowe (Ireland), 13-Brian O'Driscoll (Ireland), 12-Jonathan Davies (Wales), 11-George North (Wales), 10-Jonathan Sexton (Ireland), 9-Ben Youngs (England, 8-Jamie Heaslip (Ireland), 7-Sam Warburton (Wales, captain), 6-Dan Lydiate (Wales), 5-Geoff Parling (England), 4-Alun Wyn Jones (Wales), 3-Adam Jones (Wales), 2-Tom Youngs (England), 1-Mako Vunipola (England).
Replacements - 16-Richard Hibbard (Wales), 17-Ryan Grant (Scotland), 18-Dan Cole (England), 19-Tom Croft (England), 20-Sean O'Brien (Ireland), 21-Conor Murray (Ireland), 22-Owen Farrell (England), 23-Alex Cuthbert (Wales)