By Oliver Trust

BERLIN, June 22 (Xinhua) -- With only two weeks until pre-season training on July 8, times for Bayern supporters have been far from relaxing. Many of the 2013 treble winners' fans are deeply concerned about their side's transfer inactivity.

Used to the club operating in the German transfer market with impunity, this closed season has seen national rivals Borussia Dortmund making all the signings. Borussia, spurred on by a competitive last season have added a number of new faces and international competitors.

With the return of homegrown star from Bayern Mats Hummels and the additions of talented young winger Julian Brandt from Leverkusen, as well as full back Nico Schulz and winger Thorgan Hazard from Hoffenheim and Borussia Monchengladbach respectively has seen pundits tip Dortmund for next season's title.

These astute signings by Dortmund are in stark contrast to the Bavarian giants who are yet to replace legends, Arjen Robben and Franck Ribery, and Rafinha and James Rodriguez, and of course the Dortmund bound Hummels.

Leading German media outlets such as the Sueddeutsche Zeitung and the football magazine Kicker have called the Bayern decision to bank on the players signed in previous seasons as a "high-risk gamble." Die Welt also criticized the Bayern transfer policy as they felt the club was losing too much experience. The Berlin-based paper spoke about a "looming transfer catastrophe ahead."

Former German international Jerome Boateng is expected to be the next likely departure.

Until now only the French World Cup winners, Benjamin Pavard (VfB Stuttgart/35 million euro) and Lucas Hernandez (Atletico Madrid/80 million) are done deals, while the signing of 19-year-old striker talent Jann Fiete Arp (Hamburger SV/3 million) has also been completed.

According to latest news bulletins Bayern's attempt to rebuilt their squad is stalling at present. Spanish midfielder Rodrigo (Atletico Madrid) looks set to join Manchester City and their Spanish star coach Pep Guardiola.

Sane is said to be Bayern's primary target. The German international forward is currently on a huge contract at oil rich Manchester City, but Bayern president Uli Hoeness claimed to be rather pessimistic about his clubs' chances "as we talk about unbelievable sums."

While current Bayern stars such as Robert Lewandowski, Serge Gnabry and Joshua Kimmich have spoken glowingly about Sane in the past months, it could be a significant blow for the German champions if they fail in the chase for Sane. Failure could mean question marks about the once irresistable puling power of the club, especially when compared to a smaller, yet wealthier club such as Manchester City.

According to media reports, Bayern are now looking for other options such as Yannick Carrasco from Chinese Super League side Dalian Yifang FC, Adrien Rabiot (Paris St. Germain) and Turkish defender Ozan Kabak (Stuttgart) but are facing severe competition from European giants such as Juventus, Arsenal and AC Milan.