Zlatko Dalic's men recorded a 2-1 win over Iceland to finish top of Group D with a perfect nine points.
That victory also helped Argentina, which snuck into the last 16 courtesy of a 2-1 success against Nigeria.
Suker — the Croatia great who scored 45 times in 69 games for the national team — said he received plenty of thank you messages from Argentinians.
"Only Uruguay and us have nine points. We showed we don't make calculations and the image of Croatia only grew," he said. "I received messages from all over, especially from Argentina.
"From [Diego] Maradona? I don't want to name, but a lot of Argentinians contacted me, thanked me, said they believed in us."
Topping Group D helped Croatia avoid a last-16 meeting with France, with Dalic's men to instead face Denmark.
After several players were rested for the Iceland clash, Suker said Croatia would be ready for its next match.
"We are physically ready. It will be very hard against Denmark," Suker said. "The midfield will decide it and we have to play as aggressively as against Argentina."