Belgium 2 Algeria 1: Marc Wilmots praises mental strength of young Belgium squad after they overcome early setback to secure three points in opener

An early error from Jan Vertonghen allowed Sofiane Feghouli to convert a penalty but goals from Marouane Fellaini and Dries Martens saw Belgium emerge victorious

Belgium coach Marc Wilmots celebrates their 2-1 victory over Algeria (Getty Images)

Belgium came close to choking under the weight of expectation in their World Cup opener against Algeria but goals from substitutes Marouane Fellaini and Dries Mertens eventually saw them over the line.

Fancied by many to make waves in Brazil and tagged with the ominous 'golden generation' tag, Belgium were trailing to Sofiane Feghouli's first-half penalty until coach Marc Wilmots' tactical changes paid dividends.

Manchester United midfielder Fellaini levelled with a towering header before fellow replacement Mertens won it 10 minutes from time.

A relieved Wilmots praised his side's mental strength after they put a ponderous opening period behind them.

"This was a difficult game against a team that always moves backwards," he said.

"We made a very small mistake (for the penalty), but that is punished at a World Cup. You then have to show patience and we did.

"During the second half, we have shown our mental strength with this young group. The squad has made all the difference.

"What is important now is three points. First we have to recover and then put the focus on the next game against Russia."

Napoli's Mertens put in an impressive all-round display after replacing Mousa Dembele at half-time, delighting his watching relatives and putting his name firmly in the frame for the Russia match.

"It felt really good to score a goal, especially because my family was there," he said.

"(Starting on the bench) is a choice for the coach and you have to accept it, even though it was hard for me. Eventually I scored and I must be satisfied with that."

Fellaini shines as super subs change Belgium's fortunes

Algeria boss Vahid Halilhodzic hailed Fellaini's impact after he made a big impression in a target man role.

"Fellaini is a physically strong player and is one of the best in Europe with his head. He dominated the air and made the difference," said the Bosnian.

"We should not forget that Belgium is one of the strongest teams in Europe, and so physically strong."

Halilhodzic believes Algeria invited pressure by attempting to protect their lead but were unlucky not to be given a foul in the build-up to the equaliser.

"In the second half we let the Belgians play too much and we had to endure the game," he added. "When you do that it is quite natural that you'll concede goals.

"But in my eyes Feghouli was clearly fouled and the referee had to blow the whistle.

"That did not happen, and so the Belgians were away on counter-attack. The little details that make the difference."

PA