Belgium's Romelu Lukaku 'fully fit' to face Japan - Roberto Martinez

Striker Romelu Lukaku is fully fit after injuring an ankle in last weekend's win over Tunisia and should be available for Belgium's second-round match against Japan, coach Roberto Martinez said on Friday.

"Lukaku is fully fit, he trained today and has no problems. He'll be available, 100 percent," Martinez told reporters a day after resting the Manchester United target man and eight other first-choice players but still claiming a 1-0 win over England.

That victory has arguably handed Belgium the harder half of the draw than England but Martinez refused to be drawn on the potential difficulties of facing former champions Brazil in the quarterfinal. He said beating an understrength England with his reserve team had filled the squad with confidence.

"To be successful in a World Cup is not about facing the opponent that everyone expects is going to be giving you the golden key to go through," the Spaniard said, noting the travails of Germany and other top teams so far. "I don't think that in the World Cup you can be successful by trying to hope to get an easy path. We saw that in the Euros two years ago."

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The game against England also gave Martinez a chance to try out two key defenders who had been out injured for several weeks.

Martinez said Thomas Vermaelen was still suffering poor vision due to a black eye sustained in a clash on Thursday but would be back to full fitness before Monday's game.

"Thomas Vermaelen had a nasty knock over his eye [against England] -- he looked like a boxer this morning," Martinez said. Maybe that took his mind off his other [injury] problems. His vision is not perfect at the moment, because of the inflammation, but he'll be fine."

The coach also said Vincent Kompany, who entered as a late substitute, was also now fit, though it was not yet clear if he was sufficiently match-sharp to start against Japan.

"Vincent Kompany has reacted very well to the 20 minutes," that he played against England, Martinez said. "It was always the plan to give him that time against England, and he'll be ready."

Avoiding questions about Brazil lying in wait after the Japan game, Martinez stressed that his focus was on Monday and on his players continuing to enjoy their football.

"I think there is a belief; we've been undefeated for a long long time," he said of a run of 22 games unbeaten since losing to Spain in Martinez's first game in charge in September 2016.

"There is a real understanding among the players and it's an opportunity to face the best teams in the world ... I think we've done everything we can as a group to prepare ourselves."

Information from Reuters was used in this report.