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.

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 in the series it's the carnival club, 1. FSV Mainz 05...

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How they fared in 2014/15...

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It was an up-and-down campaign for Mainz last time out. The Karnevalsverein were one of four sides to go unbeaten for the first eight games of the season, as new coach Kasper Hjulmand's patient, passing philosophy appeared to be taking hold. A run of nine games without a win until the winter break, however, put the pressure on the Dane, and when the club slipped into the bottom two on Matchday 21, Swiss coach Martin Schmidt took over the reins. The 48-year-old returned to a high-pressing, aggressive approach and the threat of relegation was turned into a comfortable mid-table finish.

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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.