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: FC Schalke 04.

How they fared in 2014/15…

Thanks in no small way to a disappointing second half of the season, FC Schalke 04 saw their almost perennial berth in the UEFA Champions League substituted for a place in the UEFA Europa League, thanks to a disappointing seventh-placed finish. Schalke seemed to be stagnating under Jens Keller, but a gamble on former Chelsea FC coach Roberto Di Matteo failed to pay off and 2014/15 will go down as a season to forget for Royal Blues fans.

Ins…

Junior Caicara (r.) (PFC Ludogorets Razgrad)

  • Valid alternative to Atsuto Uchida on the right-hand side of the defence.
  • Experienced in Europe, having played for Bulgarian club Ludogorets in the Champions League last season.

What he offers: In addition to providing competition for Uchida's position, Caicara has that typical Brazilian flair combined with blistering pace on the ball and the ability to go on the overlap and deliver crosses.

Johannes Geis (1. FSV Mainz 05)

  • Already racked up 75 Bundesliga appearances at the age of 21.
  • Attracted interest from top Serie A clubs before opting for Schalke.

What he offers: Geis is not just about his stunning set-pieces, although that would be a good enough reason to sign him. He is also rated as one of the best defensive midfielders in the Bundesliga. 

Matija Nastasic (Manchester City FC)

  • Made 16 appearances for the Royal Blues while on loan last season.
  • Regarded as one of Europe’s most promising defenders when he joined Manchester City from ACF Fiorentina in 2012.

What he offers: Strength in the tackle, pace and composure – plays the ball out intelligently from the back.

Outs…

Jefferson Farfan (l.) (Al-Jazira FC)

  • Scored 39 Bundesliga goals in 170 appearances.
  • Added a further 49 assists.

Christian Fuchs (Leicester City FC)

  • Experienced campaigner with 136 appearances for Schalke and 67 Austria caps.
  • Provided 30 assists for the Royal Blues.

Tranquillo Barnetta (released)

  • Capable of playing both as a winger or as a central midfielder.
  • Scored three goals last season in just ten starts; capped 75 times by Switzerland.

To-do list…

The Schalke side sent into action by new coach Andre Breitenreiter (l.) at the start of the 2015/16 campaign is likely to have a few new additions to it yet. "It's true, we do have a lot of young players in the squad so we would like to add a bit more experience to it with our coming transfers," sporting director Horst Heldt told bundesliga.com. With Farfan's departure also now confirmed, that means another experienced player has left the nest and will need replacing. "We've had a very close eye on the market for months now and are already in talks with a few players," added Heldt.

Caicara has added some competition at full-back, but with Fuchs leaving, the Royal Blues may still be short on numbers there. The reinstatement to the first-team squad of Sidney Sam is like a new signing while Sascha Riether's arrival from SC Freiburg means they now have plenty of options in 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.