England coach Stuart Lancaster named Owen Farrell at flyhalf in place of George Ford, who started their opening win over Fiji, and former rugby league player Sam Burgess was included at inside centre.
“We were expecting that they were going to go for the same team so it threw us for a couple of days," Gatland told reporters.
"At the moment we wouldn’t mind the same dilemma of having that quality of choice because they’ve got some world-class players.”
Wales captain Sam Warburton was expecting Lancaster to use Burgess during the World Cup.
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“I knew they were going to use him at some point. He’s played some huge matches in (rugby) league. He’s a superb athlete with bags of talent."
Gatland's planning has been disrupted by injuries but he was not dwelling on the negatives after recalling lock Alun Wyn Jones, centre Jamie Roberts, winger George North and flyhalf Dan Biggar who all missed the 54-9 win over Uruguay.
Fullback Liam Williams has recovered from a knock and Tom Francis will partner Gethin Jenkins and Scott Baldwin in the front row.
"We’re just really excited about Saturday," Gatland said.
"They’re a quality team, there’s a huge amount of strength and depth.
“For us as a nation this is the biggest game for a long long time. As a team we have a huge amount of respect for England.”
Warburton promised that Wales would be trying some new moves and tactics against England.
“We’re going into a big game, we’re going to change stuff and do things nobody’s seen before,” he said.
“I think it’s probably the biggest game that we’ll play, unless we meet each other again in the final.
“This game is a must-win game, it’ll take the pressure off massively if we win.”
Team: 1-Gethin Jenkins, 2-Scott Baldwin, 3-Tom Francis,
4-Bradley Davies, 5-Alun Wyn Jones, 6-Dan Lydiate, 7-Sam Warburton (captain), 8-Toby Faletau; 9-Gareth Davies, 10-Dan Biggar, 11-Hallam Amos, 12-Jamie Roberts, 13-Scott Williams, 14-George North, 15-Liam Williams
Replacements: 16-Ken Owens, 17-Aaron Jarvis, 18-Samson Lee, 19-Luke Charteris, 20-Justin Tipuric, 21-Lloyd Williams, 22-Rhys Priestland, 23-Alex Cuthbert.
(Reporting by Ed Osmond; editing by Justin Palmer)
