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 up for scrutiny are Hannover 96...

How they fared in 2014/15...

It was a season of two halves for Hannover 96 in 2014/15. Die Roten sat in the UEFA Champions League spots after Matchday 11, with designs on a European place as the Rückrunde kicked off. A run of 15 games without a win after the turn of the year, however, left not only those hopes in tatters but also the Lower Saxons in a genuine relegation battle. A lack of goals beyond outgoing captain Lars Stindl and an unsettled defence were the main causes of their decline with only back-to-back victories under new coach Michael Frontzeck in their final two games staving off the drop.

Ins...

© gettyimages / Martin Rose

Felix Klaus (r.) (SC Freiburg)

  • Promising wide midfielder, 22
  • Made 52 Bundesliga appearances in two seasons at Freiburg, scoring seven goals

What he offers: Trickery on the flank, Bundesliga experience and huge potential for improvement

Charlison Benschop (Fortuna Düsseldorf)

  • Powerful, 25-year-old Dutch centre-forward
  • Netted 13 goals in 2014/15 and recorded a further three assists

What he offers: Goalscoring experience in Germany, powerful in the air, excellent link-up play

Oliver Sorg (SC Freiburg)

  • Sturdy right-back with plenty of Bundesliga experience, 25
  • Over 100 Bundesliga appearances to his name and formerly skipper at Freiburg

What he offers: Leadership, strong in the tackle, capable of playing in holding midfield

Outs...

© imago / Moritz Müller

Lars Stindl (r.) (Borussia Mönchengladbach)

  • Mobile 26-year-old attacking midfielder with a keen eye for goal
  • Netted on ten occasions in 2014/15 and produced countless captain's displays to help die Roten beat the drop

Joselu (Stoke City FC)

  • Stuttgart-born former Real Madrid CF youth-team centre-forward, 25
  • Eight goals last time out, although only one as he and his side struggled in the Rückrunde

Leonardo Bittencourt (1. FC Köln)

  • Explosive 21-year-old winger who offers bags of pace on the counter
  • The former Dortmund starlet picked up three assists last season

To-do list...

© imago / Kaletta

While Klaus and Sorg bring valuable Bundesliga experience, the goalscoring void left by the departures of Stindl and Joselu is a major concern for coach Frontzeck (l.). The signing of Benschop is a step towards rectifying that, although other proven forwards will have to be brought in if Hannover are to avoid a repeat of last season. Another glaring problem from 2014/15 yet to be dealt with is the defence: die Roten are covered at full-back with Sorg and Chile international Miiko Albornoz, yet a partner for Marcelo at centre-half must be a priority, particularly if Salif Sane is to be used to bolster an otherwise under-par midfield.

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.