Xhaka fired the ball in under the crossbar from distance in the 16th minute. It proved to be enough against second-division Kaiserslautern despite losing defender Odilon Kossounou to a second yellow card just before the break.

Leverkusen won the Bundesliga unbeaten, an historic feat. The only blip on the record of Xabi Alonso's team this season was losing the Europa League final to Atalanta 3-0 on Wednesday in Dublin. That ended Leverkusen's record 51-game unbeaten run across all competitions. It was its only loss in 53 games this season.

“The whole journey, the whole season was wonderful,” the Spanish coach said after doubling Leverkusen's trophy haul in just one season. “What we did this season is unbelievable.”

Alonso and his players ran to their fans after the whistle on Saturday in Berlin's Olympiastadion. They had supported the team loudly throughout, though were drowned at times by the even more vociferous Kaiserslautern supporters.

They displayed a spectacular tifo of a red devil grasping the trophy in front of a hellish background of fire and brimstone before the game. Flares sending red smoke into the sky embellished the effect – and gave an inkling of what was to come.

The stadium announcer's repeated requests to stop the pyrotechnics were met with continued indifference. The second half began to a huge fireworks display from the Leverkusen fans.

Despite the smoke above, there was little fire on the field after a long hard season. Kossounou was booked for stopping Kenny Prince Redondo's break in the third minute, then issued another yellow for a foul on Boris Tomiak in the 44th.

It didn't stop the Leverkusen machine from grinding out the win. Jeremie Frimpong should have made it 2-0 in the 75th after going past the goalkeeper.

It's Leverkusen's second German Cup title after beating Hertha Berlin's reserve team in the 1993 final. Leverkusen's other trophy is the 1988 UEFA Cup.