Bayern Munich's German head coach Hans-Dieter Flick attends a press conference at Stamford Bridge in London on Feb 24, 2020, on the eve of their UEFA Champions League round of 16 first leg football match against Chelsea. (GLYN KIRK / AFP)

BERLIN - Hansi Flick is facing the biggest challenge of his coaching career when crossing swords with Premier League side Chelsea this Tuesday evening in London.

In advance of Bayern Munich's first leg in the last-16-round of the Champions League, reports speak of a crucial quality test deciding over the future of the 55-year-old on the Bavarians bench.

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Although Flick has led the 2013 treble winners back to success and stability in the national league, it is the club's international performance that affects the club's decision regarding its next season coach

Although Flick has led the 2013 treble winners back to success and stability in the national league, it is the club's international performance that affects the club's decision regarding its next season coach.

Ahead of the first leg of the stress test against the London based side coached by Frank Lampard, rumors grow that Flick finds himself in a survival struggle against current Paris St Germain coach Thomas Tuchel.

French media reports speak of a made decision to sack their German coach latest at the end of the season due to the growing dissatisfaction of several of its stars and the clubs sporting director Leonardo.

The well-informed media Paris United said the club has already decided about Tuchel's departure next summer.

Several German media outlets speak about the battle of two factions at Bayern. While chairman Karl-Heinz Rummenigge is said to support a prominent coach such as Tuchel, the club's president Herbert Hainer is in favor of Flick.

The former German national team's assistant's contract is running out at the end of the season, with Bayern announcing officially to talk about the option of an extension not before May.

The ruling German champion's statement is seen as the apparent attempt to gain time as it seems impractical to wait that long.

Bayern's designated chairman Oliver Kahn is said to support Flick and use his growing influence as Rummenigge is due to resign at the end of 2021.

Bayern Munich's German head coach Hans-Dieter Flick (L) watches his players taking part in a training session at the club's training area in Munich, southern Germany, on Feb 24, 2020, on the eve of their UEFA Champions League last 16, first leg football match against FC Chelsea. (GUENTER SCHIFFMANN / AFP)

Bayern's former coaches Jupp Heynckes and Ottmar Hitzfeld expressed a warning not to wait too long and recommended a decision by March. "Everyone, the club, the players, and the coach need to get things done regarding the next season," both said.

Two times Champions League winner Hitzfeld said it is far from a disadvantage for Flick not to have collected any silverware. "He has been through all sorts of crucial matches as a player and an assistant. He experienced the 2014 World Cup final. He knows about crucial games," the 71-year-old commented.

Heynckes praised Flick and said: "He stands for the club's gen's like no other."

Former assistant coach Flick said he wouldn't step back to the second line again: "If they want another coach, my world doesn't break down."

Chelsea's French striker Olivier Giroud (C) attends a training session at Chelsea's Cobham training facility in Stoke D'Abernon, southwest of London on Feb 24, 2020, on the eve of their UEFA Champions League round of 16 first leg football match against Bayern Munich. (GLYN KIRK / AFP)

Reports speak of growing unrest in the club regarding the leader's reluctance. "He has got everything this club and the team need," injured German international Niklas Suele underlined. Several of Bayern's stars pressed their support for Flick.

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Disregarding the support for Flick it meanwhile seems an unwritten law in Munich: Coaches have to deliver on the international stage. "This shouldn't happen again," Rummenigge said, referring to the German record champions poor performance in last season's duel against Liverpool in the last-16-round.

"Flick hasn't been under greater pressure than now. He needs a courageous performance to secure his job; he needs guts," the tabloid Bild reported.