Niko Kovac suffered his first defeat as Bayern Munich boss as the Bundesliga champions slipped to a concerning 2-0 loss away at Hertha Berlin on Friday.

Held to a 1-1 home draw by Augsburg in midweek, the return of Robert Lewandowski, James Rodriguez and a raft of regulars failed to prevent Bayern from dropping points for a second successive outing.

They were disjointed in defence and uncharacteristically wasteful in attack as Vedad Ibisevic's 23rd-minute penalty and a shot from Ondrej Duda on the stroke of half-time gave the home side their first victory against the Bavarian giants in 15 league meetings.

It added up to a forgettable homecoming for former Hertha player Kovac, who will expect a response to this mini slump when Bayern host Ajax in the Champions League on Tuesday.

Recalled as one of seven changes, Jerome Boateng's first major act was to nod a James corner agonisingly wide of the top corner.

His next, however, was a panicked challenge on Salomon Kalou that allowed Ibisevic to convert the opener, leaving Bayern rattled.

Arjen Robben inexplicably turned David Alaba's low cross over the bar at point-blank range and the miss was punished a minute before the break, Duda emphatically meeting Valentino Lazaro's clever cut-back.

Boateng went close to reducing the deficit with another fine header beyond the hour but Thomas Kraft, deputising for the injured Rune Jarstein, reacted well to deny the Germany international.

Kovac threw on Thomas Muller, Serge Gnabry and Sandro Wagner in an ultimately fruitless search for a way back into his most alarming match in charge.

 What it means: Rotate with caution

Bayern had won four straight and scored 11 in the Bundesliga prior to Kovac's decision to field a vastly altered side against Augsburg.

Held to a point on that occasion, they were defensively disorganised at Olympiastadion despite the return of their leading names, with the regular rotation between Boateng, Mats Hummels and Niklas Sule doing few favours for any of the trio and potentially requiring a rethink, at least in the early part of the campaign.

 Duda does the job

Slovakia international Duda, in tandem with the tireless Lazaro, was a persistent threat to Bayern, who usually do a better job stifling their opponents.

It was Duda's lovely turn and lofted pass that created Hertha's opener, while the attacking midfielder exerted further match-winning influence with a well-timed run for his goal.

 Robben off the pace

On target in midweek, Robben, now 34, perhaps should have been the one to sit out this encounter.

The decorated Netherlands international made a meal of his team's best opportunity and was immediately punished at the other end. Unable to get on the same wavelength as Joshua Kimmich down Bayern's right, the veteran was hooked seven minutes into the second half.

 What's next?

Bayern's first task after midweek Champions League duty is a home meeting with Borussia Monchengladbach on Saturday, as Hertha head to Mainz.