Croatia coach Zlatko Dalic admitted his side were fortunate that Belgium missed several chances in the goalless draw on Thursday that sent the 2018 runners-up into the World Cup knockout phase.

The Croatians hung on for the point they needed to progress from Goup F behind Morocco as Belgium striker Romelu Lukaku passed up several golden opportunities to put them out late on.

"I expected a difficult match against Belgium. Belgium cannot play three bad matches in a row," Dalic said in the post-match press conference.

"We had some chances against us but it didn't change our mindset... We were lucky they didn't take their chances."

Croatia will face the winners of Group E -- containing Spain, Germany, Japan and Costa Rica -- for a quarter-final spot at the Al Janoub Stadium next Monday.

"It was a tough game to play, but that's football," Dalic added. "The most important thing for us is to recover, we are tired."

RB Leipzig centre-back Josko Gvardiol, playing in a protective face mask, made several crucial interventions as Croatia clung on -- and earned high praise from his coach.

"Gvardiol is the best defender in the world. He is only 20 so if he's not already the number one, he will become the number one," said Dalic.

Croatia still have a chance to replicate their run to the final at the 2018 World Cup in Russia where captain Luka Modric was named player of the tournament despite his side losing to France in the final.

"We are overjoyed that we are in the round of 16," Modric said.

"We deserved that with the game we played. We lived through some very difficult moments as we were playing against a great team.

"We have achieved the first goal, now let's move on. Today we showed that we are a top team, that we can play against anyone, and whoever comes next, it will not be easy against us."