Nico Williams was heavily involved in the opening three minutes, forcing Martin Jedlicka into the game’s first save before getting back to deny Milan Havel in the opposite box. Inaki Williams then curled an attempt of his own over the crossbar but Plzen looked determined to cause an upset, especially with a position in the top eight still a possibility.
Lukas Kalvach then hit a sweet strike that was stopped by Julen Agirrezabala before the hosts continued to apply pressure, with Yuri Berchiche being denied either side of Gorka Guruzeta heading over from Álex Berenguer’s corner.
Jedlicka was eventually beaten by a Dani Vivian header in the 22nd minute, but the centre-back had been in an offside position when N. Williams delivered his cross.
The hosts didn’t have to wait much longer for a legitimate opener, though, as Inaki raced forward and squared the ball for his younger brother to convert. Players from both teams were willing to put their bodies on the line with placings at stake, as Havel, Lukas Cerv, Guruzeta, and N. Williams each had a shot blocked.
While Pavel Sulc was left with a cut on his face following a challenge, Plzen initially avoided an extra blow after the break as they continued to compete well and I. Williams glanced his header wide.
The hosts eventually established a buffer in the 64th minute, though, as Yeray Alvarez threw himself at Berenguer’s floated free-kick to head it in. Plzen responded just seven minutes later when Cerv rolled the ball across to Havel, who cut inside Berchiche and curled his effort in off the post.
Sulc fronted the visitors’ pursuit of an equaliser but hit one shot wide and saw another headed behind by Vivian. They then had Daniel Vašulín sent off before Javier Martón audaciously scooped the ball over Jedlicka.
That wrapped up Athletic’s second win from their last six matches across all competitions to secure second spot in the league phase standings and automatic qualification to the Round of 16.
With this being just the second defeat Plzen have suffered in the league phase, Miroslav Koubek’s side will still be on the seeded side of the play-off draw.