Kiessling, who did not make the German World Cup squad despite scoring 40 times in the Bundesliga in the last two seasons, scored four of his goals in the first half for Roger Schmidt's team.

In a game played in Mainz, Kiessling added another goal just before the hour mark and Heung-Min Son completed the rout.

The result sets Leverkusen up nicely for next Tuesday's trip to Denmark to play FC Copenhagen in the first leg of their Champions League play-off.

Meanwhile, Mainz, who have already been eliminated from the Europa League, were sent packing from the Cup at the first hurdle, losing 5-4 after extra time to third-tier Chemnitzer.

Holders Bayern Munich go to third-tier Preussen Munster on Sunday, while Borussia Dortmund, fresh from beating Bayern to win the German SuperCup in midweek, are at Stuttgarter Kickers on Saturday.