The 19-year-old was left with far too much space as he charged into the box to head in a cross in the 62nd minute.
Havertz, among the greatest talents of his generation in Germany, had also scored twice in their 3-2 Europa League win over Bulgaria's Ludogorets on Thursday.
Leverkusen lost their opening three league games this season but their first three points were enough to lift them out of last place and into 15th.
In the other game on Sunday, RB Leipzig settled for a 1-1 draw at Eintracht Frankfurt which left them in 10th place on five points, one ahead of Eintracht.
Leipzig needed an Emil Forsberg penalty in the 53rd minute to cancel out Eintracht's first-half lead through Gelson Fernandes. Both teams have won just one league game this season.
On Saturday, champions Bayern Munich opened up a two-point lead at the top after easing past Schalke 04 2-0 for their fourth win in four games.
(Reporting by Karolos Grohmann; Editing by Clare Fallon)
Share
