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 mid August.

bundesliga.com is taking a closer look at each of the 18 top-flight clubs' summer transfer dealings so far. Next up in the series: Borussia Mönchengladbach

How they fared in 2014/15…

Last season saw a dream come true for Borussia Mönchengladbach as they clinched automatic qualification for the UEFA Champions League group stages, thanks to a third-placed Bundesliga finish behind FC Bayern München and VfL Wolfsburg. It was the crowning moment of a golden era under coach Lucien Favre, who not only has the Foals playing some of the most attractive football in the Bundesliga, but also some of the most successful. The second half of the season belonged to Gladbach as they collected more points than Bayern, considering results in 2015, and held off Bayer 04 Leverkusen for a group stage berth in the Champions League.

Ins…

© gettyimages / Adam Pretty

Josip Drmic (r.) (Bayer 04 Leverkusen)

  • Scored 17 goals in 33 games in debut Bundesliga season with 1. FC Nürnberg
  • Featured in all four of Switzerland's games at 2014 FIFA World Cup

What he offers: Excellent goals-per-minutes ratio; sharp eye for goal; tipped by former coach Gertjan Verbeek to "win Golden Boot one day".

Lars Stindl (Hannover 96)

  • Hannover captain last season
  • Scored 23 goals and set up 24 in 154 Bundesliga appearances

What he offers: Steady, consistent midfielder who can contribute as much going forward as he does defending; tireless individual who never holds back; appeared 20 times in Europa League.

Thorgan Hazard (Chelsea FC)

  • Set up seven goals in 27 Bundesliga appearances while on loan last season
  • Played in Belgium, England and France already

What he offers: Creativity as an attacking midfielder who can also drift out wide; alternative in several positions in what will be congested season.

Outs…

© gettyimages / Dean Mouhtaropoulos

Max Kruse (pictured r.) (VfL Wolfsburg)

  • Scored 11 goals for the Foals last season
  • Capped 13 times by Germany
  • Scored in double figures in each of past three seasons

Christoph Kramer (pictured, l.) (Bayer 04 Leverkusen)

  • Germany World Cup winner, appearing briefly in final
  • Missed just 5 Bundesliga matches during two-year loan spell with Foals

To-do list…

© gettyimages / Christof Koepsel

Gladbach are heading into unknown territory this season with the UEFA Champions League providing at least six additional fixtures up to the winter break, so finding the right balance between Europe and the Bundesliga may be the main challenge, requiring a bit more depth in the squad. Stindl has come in for Kramer and Drmic for Kruse, but the numbers are yet to be swollen. "When we sign a player, we always want to sign somebody who is hungry and who will improve as a player here," said sporting director Max Eberl (l.), confirming that they will not just buy for the sake of it. Promotion from within, such as with Marvin Schulz, Mahmoud Dahoud and summer signing Djibril Sow, may therefore be the solution to the lack of numbers.

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.