Norwegian teenager Antonio Nusa scored on debut to take RB Leipzig past Bochum 1-0 at home on Saturday, while last season's surprise runners-up Stuttgart lost 3-1 at Freiburg.
Nusa, 19, was brought in to replace Barcelona-bound Dani Olmo this summer, scored just four minutes after coming on, thumping a long-range effort through a crowded penalty box to give Leipzig the lead.
Leipzig, German Cup winners in two of the past three seasons, were forced to sweat late when captain Willi Orban saw red for a last-man foul on Myron Boadu with five minutes remaining.
Stuttgart, fellow Champions League participants alongside Leipzig, Stuttgart lost 3-1 at a Lukas Kuebler-powered Freiburg.
New Stuttgart striker Ermedin Demirovic, brought in to replace the Borussia Dortmund-bound Serhou Guirassy, opened the scoring with an acrobatic effort two minutes in.
Kuebler levelled things up with a low, long-range strike in the first half and Freiburg took the lead early in the second when Ritsu Doan's messy effort dribbled across the line.
Kuebler's 61st-minute header put Freiburg in control in their first match since the departure of long-term manager Christian Streich, who left the club after 13 years in charge in the summer.
Union Berlin snatched a point at Mainz, a 74th-minute rocket from Laszlo Benes cancelling out Nadiem Amiri's first-half goal for a 1-1 draw, with former Mainz manager Bo Svensson now in the Berlin dugout.
Union played Champions League football last season but only avoided relegation in the final match.
A hat-trick from forward Andrej Kramaric, including a penalty, a header and a close-range strike, took Hoffenheim to a 3-2 win over promoted Holstein Kiel.
Kiel, playing their first ever season in the top division, were reduced to 10 men on 82-minutes when Andu Kelati picked up a second yellow for a lazy challenge.
Augsburg held Werder Bremen to a 2-2 draw at home, Elvis Rexhbecaj and Samuel Essende scoring for the hosts and Felix Agu and Justin Njinmah goaling for the visitors.
In Saturday's late game, last season's Champions League finalists Dortmund host Eintracht Frankfurt.
