Dries Mertens: Scoring Belgium's opener vs. Panama was a 'big relief'

Dries Mertens said it was a "big relief" to score his fine volley that put Belgium on their way to a 3-0 win over Panama to open the World Cup.

Belgium were frustrated for the first 45 minutes but Mertens broke the deadlock two minutes after the restart with a superb shot into the opposite corner beyond a helpless Jaime Penedo in the Panama goal.

"The first goal was a big relief for everyone. It was really difficult," Mertens said after the game. "You know when you begin at a World Cup after a long preparation and then it's finally that first game coming -- everyone expects a lot."

Belgium are among the favourites to lift the trophy in Russia and looked the part against the debutant Central Americans, but coach Roberto Martinez cautioned that the result didn't change the Red Devils' outlook.

"In the end, we have three points and now we can focus on Tunisia," Martinez said. "We're not getting more and more the favourite for winning this tournament after this 3-0-victory. Every game is different."

Martinez also hailed his team for waiting for their chances after failing to find the net in the first half.

"An introduction to a World Cup is always a special but difficult moment," Martinez said. "Panama played really well organised. We needed to be patient. We couldn't get frustrated.

"In the second half we had the quality of Dries Mertens, Eden Hazard, Romelu Lukaku and Kevin De Bruyne to make the difference. The team spirit was good. We needed to open the game more, but we defended really well. Everyone took his responsibility."

Martinez believed his side "adapted really well" to the conditions, with the humidity at about 75% in Sochi, and Mertens said it was also hard to shake off the rust.

"You have a lot of energy to run, but it just didn't work out. I had, surprisingly, really heavy legs," he said. "You see this at every team in the first game of a tournament. Hopefully the second game will be better."

Panama coach Hernan Dario Gomez praised his side's gritty performance but said the five yellow cards they picked up will not stop his team adopting a similarly rugged approach when they face England.

"It is a result that can't be positive because we lost 3-0 but they could have won by a landslide," Gomez told reporters. "When you consider where their players play and where our players play the difference wasn't that great. I think we did a good job. Some people thought we would lose by seven goals but it was only 3-0."

The game was marked by 35 fouls and eight yellow cards, five for Panama and three for Belgium but neither side could be accused of dirty play and Gomez said England could expect more of the same in Nizhny Novgorod on Sunday.

"We are a team that is very organised, we play tactically," Gomez said. "Sometimes we may look tough but the other teams are tough and physically strong as well. You know the English team are strong, they can play even 100 minutes and we have to fight to manage 90 minutes at the same pace the Europeans play."

"We will try to recover and we will keep growing and playing with dignity."

Information from Reuters was used in this report.