Belgium coach Marc Wilmots praised his side's mental strength after they narrowly averted a shock defeat by Algeria.The African side were on course to record a surprise victory over the well-fancied Belgians, Sofiane Feghouli giving them a 25th-minute lead from the penalty spot which lasted until 20 minutes from time.Wilmots can take some of the credit for the turnaround after two of his substitutes - Manchester United's Marouane Fellaini and Napoli's Dries Mertens - scored the goals that turned defeat into triumph.But he was keen to praise his charges for negotiating their way through a trickier than expected contest. "This was a difficult game against a team that always moves backwards," he said. "We made a very small mistake, 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." Wilmots faces some selection posers ahead of the next Group H match against Fabio Capello's Russia, with both goalscorers pressing for starts and the likes of Adnan Januzaj and Kevin Mirallas left unused against Algeria. Looking ahead, he said: "What is important now is three points. First we have to recover and then put the focus on the next game against Russia. "We will be looking to continue to build on this momentum." 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." Algeria boss Vahid Halilhodzic felt his side invited pressure by dropping too deep at 1-0, but was aggrieved by the winning goal. Kevin de Bruyne made a strong tackle on Feghouli to set the move in motion and Halilhodzic believes the referee should have awarded a foul. "In the second half we let the Belgians play too much and we had to endure the game. 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." Halilhodzic was full of praise for the opposition, with Fellaini's physical threat particularly impressing him. "Despite the defeat, the players have my congratulations, because they gave everything," he said. "Algeria should be proud. We should not forget that Belgium is one of the strongest teams in Europe, and is physically strong. "Fellaini is a physically strong player and is one of the best in Europe with the head. He dominated the air and made the difference."