Roberto Martinez had reassuring words on Romelu Lukaku's status and even attempted to put a positive spin on Belgium's 4-1 defeat to the Netherlands following the stunning reverse.

Belgium are the world's second-ranked side but were completely outclassed on home turf by a team they had not lost to since 1997.

It had still been 0-0 when Lukaku hobbled off in the first half, however, with the Chelsea forward trying and failing to play on after sustaining an injury in a tangle with Nathan Ake.

However, with three more Nations League matches to come this month, Martinez could at least inform fans Lukaku's ailment was not as serious as might have been feared.

"Lukaku's problem was a knock," he said, although he accepted: "From then on, it became a more difficult match."

This was far from an ideal result in Belgium's first competitive match of a World Cup year, but Martinez believes his side can benefit from the experience.

"This is what we needed to prepare for the World Cup," he said. "It's a hard result, but it's clear what we need to work on.

"The World Cup does not start until November, but with the national team it is already within 17 days. We will have to work in a specific way."

The former Everton manager added: "It is clear what we need to work on. We have to use the Nations League to prepare for the World Cup.

"We started well and found spaces. After that, it became physically difficult for players who didn't play much. The result is the result of all these aspects."

Jan Vertonghen disagreed, however, with the Belgium defender identifying issues that were not purely physical.

"It's a very painful defeat," he said. "We didn't get off to a bad start, though. We made it through a few times, especially via the left side.

"We lacked momentum after Romelu's substitution. The Dutch have had just as tough a season as we have. That shouldn't be an excuse. The physical part is not tonight's shortcoming.

"In particular, we had difficulties controlling the deep striker.

"This defeat puts us with both feet on the ground. It is clear that we will have to keep working hard."

Belgium full-back Timothy Castagne has been ruled out for the remainder of Euro 2020 after sustaining a double fracture of his right eye socket.

Roberto Martinez's Belgium opened their Euro 2020 campaign with a comfortable 3-0 win over Russia on Saturday but it came at a cost.

Castagne and Russia's Daler Kuzyaev collided in mid-air after 25 minutes and both went down holding their heads.

Belgium's Castagne was substituted immediately and Kuzyaev two minutes later in the Group B clash in St Petersburg.

"Really bad news, really sad news to see Timothy Castagne is going to be out of the tournament," Belgium head coach Martinez said. 

"He's had images taken, he's got a double fracture and now we'll take the necessary treatment."

While Leicester City's Castagne will sit out the rest of the European Championship, the news was better for Jan Vertonghen. 

Veteran defender Vertonghen was withdrawn in the 77th minute due to ankle injury, but Martinez said there were no major concerns regarding his fitness going forward. 

"Vertonghen has got just a typical football injury, an ankle knock that we're probably going to wait 48 hours to see the real extent, but I don't expect it to be too serious," Martinez said. 

Overall, Martinez was satisfied to see his side play the way they did in the opener. 

"The performance is very pleasing," he said. "It's never easy to start a tournament of this magnitude and I think it looked a team very concentrated for 90 minutes, kept a clean sheet in a very good way, and then obviously the win will allow us to grow and to get into the tournament."

Belgium are unbeaten in 10 games in all competitions (W8 D2) and have suffered just one defeat in their last 24 internationals (W20 D3), via a 2-1 loss to England in the Nations League in October 2020.

Russia boss Stanislav Cherchesov will have far more to worry about after an uninspiring performance but expressed optimism his side will bounce back against Finland on Wednesday.

Cherchesov's Russia have lost four of their last six competitive games (W2) after losing just one of their 13 before that (W10 D2).

"We are still in the tournament," Cherchesov told a news conference. "We chose our system, which worked partially but then started to break down. The Belgians scored and then it was difficult to get the ball off them."

"We will get out of the situation. We put ourselves there, so now we must find a way out."