Steven Gerrard revealed how the England players had suffered in the second half as the intense heat took its toll during their 1-0 win over Paraguay in Frankfurt.
England got off to a flying start with a Carlos Gamarra's own goal from David Beckham's third-minute free-kick but, after a bright first-half performance, they faded badly after the break.
'It was very difficult out there,' Gerrard told ITV. 'There were a lot of players suffering with blisters. It was very hot.
'But we've got some days now to recover. Our next few games are in the evenings when it will be cooler and that will suit us better. You'll see an improvement I'm sure.
'It was disappointing that we weren't two or three up by half-time. In the second half we came under pressure but we stuck together but we're happy with the clean sheet and the win.'
Gerrard, asked about Michael Owen's withdrawal in the second half, added: 'Michael worked very hard for an hour. He is fighting for that match fitness and I'm sure it will come very soon.'
Chelsea midfielder Joe Cole, who was taken off with eight minutes remaining, is confident England will find it easier to cope with the evening kick-offs for the remaining Group B games against Trinidad and Tobago and Sweden.
'It was hotter than Portugal (during Euro 2004),' said Cole on BBC Radio Five Live. 'We'll be praying for some cold and damp weather over the next few weeks. Evening kick-offs will help us.'
'There were huge expectations and, coupled with the weather, it was a good performance, especially in the first half, and a fighting performance in the second half.
'I don't think they had many chances, it was a good performance. Now we can look forward to Trinidad and a win should get us through.'
Beckham blamed England's fading performance on the heat rather than the manager's decision to take off Owen.
He told BBC1: 'You don't realise how hot it was out there.
'We were good at times but we gave away the ball too much. It was hot and we got what we wanted. That was a good start and we have the three points.
'The performance could be better but we will work on that. We set out to get the three points and we did that.
'We let them (Paraguay) pass the ball around too much. But we were exhausted. We can put it down to that (the heat) because we are usually strong and our fitness levels are high.'
Looking ahead to the next match, Beckham predicted a later kick-off - 6pm (5pm BST) in Nuremberg on Thursday - might suit England better.
'We will be alright. This was a three o'clock kick-off. It was 28 or 29 degrees out there,' he said.
'We must perform better better and play better but we got what we wanted.'
Frank Lampard stressed the result was more important than the performance.
He told BBC1: 'The heat sapped us a bit in the second half - but to get three points in our first game is the important thing.
'We know we can do a bit better but we've got a bit of time to work on things - and we'll get better.
'Once the dust settles we'll see what an important result this is.'
He continued: 'We started really well with great intentions, moved the ball really well and got a goal.
'We were upset at half-time we hadn't got another.
'Paraguay are more used to this climate and we sat back a bit and suffered under pressure - but we defended well and that's a big plus for us today.'
Lampard admitted there had been a few nerves towards the end of the match as faltering England held on to their slender lead.
He told ITV: 'You are never 100% confident when you're 1-0 up but we've got the three points in the bag and hopefully we can push on from here.'