Union Berlin coach Urs Fischer hailed an "amazing" achievement as his side stunned top-four hopefuls Freiburg with a 4-1 win on Saturday to seal a top-seven finish on a dramatic day in the Bundesliga's race for Europe.

"It's amazing what the lads have managed to do this season," Fischer told Sky, after his side secured European qualification for the second year in a row.

Minnows Freiburg and Union have both been flying high this season, but it was the side from the capital who soared on Saturday as they smashed in three first-half goals to put themselves on course for the Europa League in sixth and dent Freiburg's hopes of a fairytale Champions League berth.

Freiburg remain in fourth, but will drop out of the Champions League places if RB Leipzig beat Augsburg on Sunday.

Union, who were only promoted in 2019, still have an outside chance of reaching the Champions League, having moved within a point of Freiburg with one match remaining.

"It's incredible what we are managing to achieve year on year as such a small club," said Union midfielder Grischa Proemel.

Proemel gave Union the lead early on, bundling the ball over the line from close range after Taiwo Awoniyi's effort hit the post.

Lucas Hoeler had an equaliser ruled out for handball before Union captain Christopher Trimmel headed in Sheraldo Becker's cross on the half-hour mark.

Becker then rampaged down the right wing to give his side a 3-0 lead at half-time and leave the home fans shellshocked.

Hoeler gave Freiburg fresh hope on the hour mark when he wriggled free of the back line to poke a long ball into the bottom corner.

But substitute Andras Schafer added a fourth for Union to end any hopes of a home comeback.

While Freiburg were left to a rue a missed opportunity, third-placed Bayer Leverkusen secured Champions League qualification as Czech striker Patrik Schick fired them to a 4-2 win at Hoffenheim.

French striker Georginio Rutter gave Hoffenheim an early lead after a mistake from Leverkusen defender Piero Hincapie.

Schick then brought the visitors level with an elegant, first-time finish, but Christoph Baumgartner restored the lead with a header just two minutes later.

Yet Leverkusen turned the game on its head with two goals in three minutes in the second half.

Moussa Diaby slotted in an equaliser on 73 minutes, and Schick danced through the box to make it 3-2 moments later before Lucas Alario struck in stoppage time.

"We are really happy. We missed out on the Champions League in the last two years, so it was our big goal this season," Leverkusen sporting director Simon Rolfes told Sky.

Hoffenheim's defeat means that Cologne are also effectively guaranteed European football next season with a top-seven finish, despite losing 1-0 at home to Wolfsburg.

Former Cologne player Yannick Gerhardt scored just before half-time to give Wolfsburg an unexpected win, but delirious Cologne fans still invaded the pitch to celebrate at full-time.

At the other end of the table, relegation-threatened Hertha Berlin missed the chance to clinch survival with a 2-1 defeat at home to Mainz.

Hertha goalkeeper Marcel Lotka allowed a Silvan Widmer shot to slip through his fingers to give Mainz the lead in the first half.

Davie Selke levelled the scores with a penalty on the stroke of half time, before Stefan Bell rose high at a corner to head home a late winner for Mainz.

Hertha can still reach safety this weekend if Stuttgart lose to Bayern Munich on Sunday.

Elsewhere, Borussia Dortmund cruised to a 3-1 win against relegated side Greuther Fuerth to secure second place.

Jessic Ngankam cancelled out Julian Brandt's first-half opener with a delicate chip on 70 minutes, but Brandt immediately restored the lead at the other end and Felix Passlack added a third shortly afterwards.