The 2019 world champion kicked off the 21-stage event by winning the opening 3.3km Tartu Vald test but is sitting last in the overall standings after being hit with a five-minute penalty following an enforced engine change after shakedown.
Facing an uphill struggle to score championship points, Tanak highlighted what could have been by winning the spectator stage by 0.6s from Toyota’s Elfyn Evans and Hyundai’s Esapekka Lappi, who clocked identical times.
“I would say that the more I have to go through the day, the more it hurts," said Tanak at the stage end.
“It's getting more and more painful. Our chances for the championship were quite tight considering our performances this year and we were working hard for the next two rallies.
“This was a proper kick in the balls.”
By virtue of Tanak’s penalty, Evans and Lappi will head into Saturday with a shared 0.1s lead over championship leader and Toyota driver Kalle Rovanpera, who opted for a measured start to the rally.
"I didn't stress too much about this one, it's a tricky stage so we just did a clean run-through with no push,” said Rovanpera.
“Tomorrow is going to be interesting, opening the road will be a big challenge it seems, there is a lot of loose gravel on the road on Friday's stages. We need to do our best and see where we are tomorrow.”
Hyundai’s Thierry Neuville ended the stage 1.6s adrift of the pace but ahead Toyota’s Takamoto Katsuta and Teemu Suninen, who made his Rally1 debut driving the third Hyundai i20N. M-Sport’s Pierre-Louis Loubet completed the eight-car Rally1 field.
Toksport Skoda driver Andreas Mikkelsen assumed an early lead in WRC2 by 0.3s from Oliver Solberg, who lost time to half spin and slight overshoot in the stage.
WRC2 rival Emil Lindholm was fortunate to reach the stage end after damaging his left rear suspension on his competitive debut for Hyundai’s Rally2 squad.
The rally continues on Friday with crews set to face seven more stages, comprising 133 kilometres of competitive action.