Karlsruhe --

Jerome Boateng was sent off as Bayern Munich went down 2-1 at second division Karlsruhe as the German champions prepare to return to league action next Friday. Arturo Vidal leveled the scores with a great finish on 20 minutes following Boubacar Barry's early goal on the break. Pep Guardiola's much-changed side looked rusty and out-of-sync in their first 90 minutes of the new year.

Half-time substitute Boateng was dismissed with 18 minutes to play, bundling over Erwin Hoffer with only Manuel Neuer to beat. Dimitrij Nazarov converted to give Karlsruhe an excellent win in preparation for their own second half of the campaign.

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Winter training has been decidedly low-key from the league-leaders who hold an eight-point lead over Borussia Dortmund in the Bundesliga. Bayern's only friendly of this winter break was scheduled more than a year ago when Tim Walter, Karlsruhe's then-U19 coach, changed hands. Walter has taken over Bayern's U17 side, the 'Winter Champions' of its regional division with 13 wins from 15 games.

That switch might not seem significant, but Karlsruhe and Bayern have a long association of transferring players that goes back to the 1980s: Oliver Kahn, Michael Tarnat, Thorsten Fink and Mehmet Scholl were all developed by KSC before going on to domestic and European success in Munich.

Indeed, according to the history books, Karlsruhe was where the first recorded game of association football took place in Germany. The local team, Karlsruher FV, was the preeminent German side until the outbreak of the First World War, which essentially decimated the country's early football links.

Out of the Bundesliga since 2009, Karlsruhe is best known for its glory days in the early 1990s where the club rubbed shoulders with some of Europe's greatest clubs. Coached by Winnie Schäfer, the current coach of Jamaica, KSC beat PSV Eindhoven, Porto and Bordeaux and smashed Valencia 7-0 in the match remembered as the 'Miracle of the Wildpark'.

But recent stints in the second and third-tier are understandably a source of frustration. Karlsruhe was edged out to promotion last season by Darmstadt, but it was compounded by agonizing defeat to Hamburg in the relegation/promotion playoff – the Northern Germans scored a controversial injury-time equalizer and won in extra-time.

Bayern started with four changes from its last competitive match against Hannover in December – Thomas Müller, Jerome Boateng and Thiago Alcantara dropping out. Most encouraging was the return of Douglas Costa to the side, the Brazilian flanking Robert Lewandowski to the left, whilst Kingsley Coman played to the right.

The hosts threatened as early as the seventh minute: Enrico Valentini tossed the ball hopefully into the box. Manuel Neuer was beaten to the ball by Dimitros Diamantakos whose finish was narrowly past the target. Lewandowski was inches away from connecting with Coman's cross on 13 minutes, but the second-division side would draw first blood on the counterattack.

Javi Martinez lost his footing on the right-side two minutes later, allowing Boubacar Barry to take charge of the ball. But the youngster's precise finish from 20 yards was an explosive effort from the Guinean hotshot who has been capped by Germany at U19 level.

Bayern's combination play wasn't quite so slick in the first half, but the equalizer on 20 minutes showed the league-leaders' capability to turn the rudimentary, lateral possession into goals. Costa's forceful ball through the lines found Vidal in space and the Chilean midfielder bent the ball superbly into the top corner.

Rafinha, Boateng, Joshua Kimmich, Thiago, Thomas Müller and Arjen Robben were introduced at the break as Guardiola looked to hand out as much appearance time as possible ahead of the Hamburg clash next Friday. Coman's curling effort immediately after the restart was just lacking in accuracy, whilst Robben passed up a one-vs-one chance, choosing to shoot with his left-foot when the situation demanded a simple right-foot finish.

As Guardiola tinkered, introducing a clutch of homegrown youngsters, Karlsruhe looked the more assured team in possession. Manuel Torres almost replicated the earlier effort from Vidal, but his shot struck the inside of the post on 61 minutes. Nazarov's finish with just Neuer to beat was tepid, whilst Torres headed wide on 65 minutes.

Karlsruhe was awarded a decisive spot-kick on 71 minutes when Boateng misjudged the long ball, letting Erwin Hoffer sprint clear on goal. The German defender nudged him outside the box and Hoffer went down inside the area, winning the penalty kick, which ultimately saw the Bayern player dismissed. Nazarov converted the kick from 12 yards – and with a third-string side, at best, the visitors had little response.

Defeat in Karlsruhe means practically nothing for the German champions. Guardiola's side are one of the winter break winners in the Bundesliga with several players returning from absence and another trio – Benatia, Götze and Ribery – expected to return in February. Bayern's return to competitive action kicks off the second half of the Bundesliga season with an away trip to Hamburg on Friday January 22.