Highly rated prospect Kaapo Kakko scored a hat trick to lead Finland over host country Slovakia at the Steel Arena. Petteri Lindbohm scored the other tally for Finland, while Erik Cernak and Martin Marincin replied for Slovakia.
Tatar, who had scored in his team's win against the United States on Friday, was held off the scoresheet. He finished with an even differential and three shots on net in 14:29 of action against Finland.
Slovakia has the day off on Sunday. Their next game is slated for Monday against Canada at 2:15 p.m. ET.
Elsewhere at the Worlds, Habs prospect David Sklenicka played in the Czech Republic's 7-2 win over Norway on Saturday. He didn't register any points but finished with a plus-1 differential and one shot on net in 16:03 of ice time.
The Czech Republic also have a day off on Sunday before facing Russia at 10:15 a.m. ET on Monday.