England [Images] will have to play better than they did in Saturday's 1-0 win over Paraguay if they are to win the World Cup, said coach Sven-Goran Eriksson.

England got the points with an early own goal by Paraguay captain Carlos Gamarra but toiled in the heat against South American opponents who did a far better job of keeping the ball.

• England toil to beat Paraguay | Images

"I know that to win the World Cup we have to play better football, but we will play better football," Eriksson told a news conference after the Group B opener.

"I'm sure we will play better and better every game. I think it was very important to get the three points."

As for his ambitious side's display, he said: "In the first half, the first 35-40 minutes we did well, played the football we should have played and could have scored more goals.

"But in the last minutes of the first half and for long periods of the second half we suffered to keep the ball. There was a lot of possession for Paraguay.

"In football, you suffer and it was good to see the team suffer, hang on and get that result," said the Swede.

STEAMY DAY

Eriksson said the temperature had affected his team and was reminiscent of the steamy day at Shizuoka when they were dumped out of the 2002 World Cup by Brazil [Images] in the quarter-finals.

"The heat knocked us a little bit," he said. "It was the first time we'd faced temperatures like it was today.

"The players said it was hot like against Brazil in Japan [Images] four years ago."

Eriksson, who took striker Michael Owen [Images] off after 55 minutes, explained the surprise move by saying: "I wanted to see some fresh legs on the pitch.

"I wanted Joe Cole as a link between Peter Crouch and the midfield. We tried to have five in midfield and only Crouch up front and it got better in the end. I think Michael Owen did well and will get better and better."

The real praise was for the England rearguard, in which central defenders Rio Ferdinand and John Terry stood out.

"Our defence was great," Eriksson purred. "Even if Paraguay had the ball a lot, they didn't create many chances. I'm extremely pleased."