Marc Wilmots praised his Belgium side for showing patience as they came from behind to narrowly defeat Algeria 2-1 in their opening Group H match.
Algeria were on course to record a shock victory over the highly-rated Belgians as Sofiane Feghouli gave them a 25th-minute lead from the penalty spot which they held 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."