The hosts led from Lucas Hoeler's third-minute opener and things looked grim for Leverkusen when defender Sven Bender was shown a red card for bringing down Hoeler.

But the dismissal was nullified after a video review because it wasn't a last-man foul and Alario made the best of the reprieve to turn matters around before half-time.

First, he pounced on a terrible pass from Freiburg's Nicolas Hoefler in the 29th minute before netting again three minutes before the break.

Nadiem Amiri made it 3-1 from long range in the 64th minute, Nils Petersen revived Freiburg's hopes, but Germany defender Jonathan Tah's 76th-minute header sealed the points for the visitors.

Leverkusen, with three wins after three opening draws, now lie fourth, three points off the top spot shared by champions Bayern Munich and Borussia Dortmund.

Australian Associated Press