Cologne - While the Bundesliga's many stars continue to build up their fitness levels ahead of the new season, clubs up and down the country are working tirelessly behind the scenes to strengthen their playing staff in time for the big kick-off in August.

Over the next few weeks, bundesliga.com will be taking a closer look at each of the 18 top-flight clubs' summer transfer dealings so far. Next under the microscope, it's Hertha Berlin...

How they fared in 2014/15...

It was a campaign of toil for Hertha in 2014/15 as the Old Lady ended the season in 15th, above the relegation play-off place only on goal difference. With two wins in their final ten games, the capital club avoided relegation more by virtue of others' failings than by their own strengths. Only two clubs scored fewer goals last term than Hertha, but after Pal Dardai took over from Jos Luhukay in February, there were promising signs of creativity from Valentin Stocker and marked defensive improvement. Ivorian international Salomon Kalou disappointed in his debut Bundesliga season, only managing one goal in the Rückrunde and six overall.

Ins...

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Mitchell Weiser (r.) (FC Bayern München)

  • 21-year-old, comfortable playing at right-back or on the right of midfield
  • Scored one goal and made four assists with the champions last season

What he offers: Creativity, versatility and excellent crossing ability

Outs...

© gettyimages / Martin Rose

Marcel Ndjeng (r.) (SC Paderborn 07)

  • Reliable full-back also capable of playing in midfield, 33
  • Netted one goal for die alte Dame in 2014/15, a free kick at 1. FC Köln on Matchday 10

To-do list...

While the arrival of Weiser means Hertha are well stocked out wide, sporting director Michael Preetz may be looking to strengthen the spine of the side. A high-class centre-half to partner the reliable USA international John Anthony Brooks will be top of his shopping list, while with Hajime Hosogai and Jens Hegeler struggling to make an impact in 2014/15 Preetz will also be on the lookout for a new partner for Per Skjelbred in central midfield. A proven goalscorer to improve on the club's meagre returns last campaign would be an added bonus.

Editor’s note: Not all summer transfers will be discussed here. The players featured in this article made at least ten league appearances for their respective clubs last season, chipped in with numerous goals and assists or made other significant contributions to their team. For an overview of the 2015/16 summer transfers, click here.