Luka Modric said Croatia "cut off" Lionel Messi from the ball but insisted his side's 3-0 win over Argentina was not as straightforward as it appeared.

Croatia limited Messi to only one shot after the Argentina talisman took 11 in their first game, a 1-1 draw with Iceland, and Modric said it all went according to plan.

"This result and Argentina's poor display was due to our good game, our compact block all over the pitch, particularly when we didn't have the ball," Modric said in his postgame news conference.

"We cut off Messi, stopped him receiving the ball. He's their most dangerous player."

Modric and his teammates also reduced Messi's touches in the penalty area from nine to two, and cut the number of passes he received in the attacking third from 45 against Iceland down to 10.

"Messi is an incredible player, but he can't do everything alone," Modric told Argentina's TV Publica. "In football you need help and it can't be done alone. Although he is great, great, but it can't be done alone.

"The way we played helped today too. We closed the gaps so [Javier] Mascherano couldn't pass the ball in the beginning, and then later when we got our rhythm of the game, we played very well."

World Cup 2018 must-reads

- Make your daily picks with ESPN FC Match Predictor 2018!

- World Cup fixtures, results and coverage

- World Cup LIVE: Follow all the action on and off the pitch each day with ESPN

- Mexico trio and Ronaldo make the ESPN team of Round 1

- Who can qualify for the round of 16? World Cup permutations

Argentina boss Jorge Sampaoli admitted Croatia's tactics to deny Messi were effective.

"Our driving force is Leo, but weren't able to find him," Sampaoli said. "We work all the time with the aim of getting Leo the ball, but our opponents work all the same to try and make sure it doesn't reach him."

Croatia's opening goal came after a woeful mistake by Argentina goalkeeper Willy Caballero, and Modric added one of his own with a belter from distance in the 80th minute, before Ivan Rakitic added a third in stoppage time.

Lionel Messi had trouble getting on the ball against Croatia. Maja Hitij/FIFA/Getty Images

But Modric said the scoreline was a bit misleading and that Caballero's error gave his team a second wind.

"In the end, our victory looks easy, but it wasn't that easy. I think the win was fully deserved, but it wasn't easy," he said.

"That first goal, in the second half, followed a mistake. It was a shot in the arm for us. We played a perfect game and you need a perfect game to beat such a great team."

Croatia booked their place in the knockout stage for the first time since 1998, but Modric called for calm and declined to look past their final game against Iceland, who play their second game Friday.

"The most important objective has been realised. We've got to take it game by game, let's not get ahead of ourselves," Modric said. "This win will boost our confidence for the coming games.

"It's going to be tough, but let's avoid euphoria, give it a wide berth and keep our feet firmly on the ground to prepare for the next matches."

Croatia coach Zlatko Dalic also cautioned his squad against getting carried away.

"We have to be happy, we have emerged from the group. We have beaten great Argentina with the greatest player in the world, Messi," Dalic said. "However, we have to pray to God we don't go over the top. We have to be humble, dignified, put in a good shift as a team. No one is happier than I am, but I have to keep calm and composed, feet on the ground."