The Irishman trailed the man who replaced him at M-Sport Ford for the first half of the day before unleashing an early afternoon attack on the Estonian, establishing control as his low starting position offered superior traction on the increasingly rutted second pass.
He outpaced the entire field by 7.8sec on Brattby 2 to go in front, then extended his buffer to 10.5sec with another benchmark time on the very next test. Tänak, however, fought back as darkness fell, reducing the overnight deficit to just 2.6sec.
Breen, who is contesting a part-programme aboard a Hyundai i20 N this season, was unperturbed by Tänak’s late charge.
“It’s definitely been one of my strongest days,” he grinned. “Last year I was usually upside down or stuck in a hedge somewhere, so it's music to my ears to be in the lead tonight. It's the Mad Hatter's Tea Party and we're all invited - I can't wait for tomorrow!"
Although Tänak’s pace represented a significant step-up compared with last month’s Rallye Monte-Carlo, the Estonian was not overly positive at close of play. He was pushing his Puma to the absolute limit but felt like the stage times didn’t reflect this.
"Result-wise, we can definitely be quite happy. It's much more than we expected coming here. But the thing is that we could be a lot better."
Esapekka Lappi made it two Hyundai cars inside the top three with a solid drive on his second rally for the team. A high-speed spin after overshooting a junction on SS6 was the only real slip-up for the Finn, who trails Tänak by just 8.6sec heading into day three.
A further 15.3sec behind in fourth overall was Elfyn Evans, the highest-placed Toyota Gazoo Racing driver. He initially struggled for confidence on the fast-paced stages but improved throughout the day, surviving a brush with an infamous snowbank while climbing the leaderboard.
Evans’ ascent was partially aided by the fact that team-mate Takamoto Katsuta rolled his GR Yaris on the second pass of Brattby. The Japanese hotshot retired shortly afterwards with radiator damage, putting an end to what had been a promising start.
Kalle Rovanperä, leader following Thursday night’s opener, dropped down the order after spending the day on road-opening duties. Grip was hard to come by for the defending champion as he swept a clean line in the loose snow. He trailed colleague Evans by just 4.6sec.
Sixth overall wasn’t where an under-the-weather Thierry Neuville had intended to be after the first eight stages, but the Belgian could do no more as he battled with understeer on his Hyundai. Superficial damage to the front and rear aero - inflicted by various run-ins with snowbanks - didn’t help matters.
Pierre-Louis Loubet made some major strides in his Puma, gaining confidence with every stage as he got to grips with snow and ice. A top-two time on SS5 was proof of the Frenchman’s development and he arrived back to Umeå a respectable seventh overall.
The remainder of the leaderboard consisted of WRC2 stars, with Oliver Solberg, Sami Pajari and Jari Huttunen completing the top ten.
Saturday is the longest day of the rally and features seven tests totalling 126.22km.
- Full coverage from Rally Sweden is available on WRC+ All Live here, including every stage broadcast as it happens as well as key interviews, features and expert analysis from the service park.
Finland
Italy
Hungary