After struggling to assert himself at VfL Wolfsburg during the first half of the 2013/14 season, Ja-Cheol Koo opted for a mid-season move to 1. FSV Mainz 05.
The South Korea captain was restricted to just eight league starts for the Wolves since returning from an 18-month loan spell at FC Augsburg, but Koo proved to be a revelation for die Fuggerstädter during his time at the SGL Arena club, inspiring them to safety in both the 2011/12 and 2012/13 seasons.
Koo had already made a name for himself back home in South Korea after being called up to the national team only a year into his professional career. Blackburn Rovers saw him in action and were close to luring him to the Premier League in 2010, but the move did not materialise. Blackburn's loss was Wolfsburg's gain as they were able to bring negotiations with Koo's club Jeju United to a successful conclusion just a year later.
The South Korea international had the misfortune of arriving at a club who were fighting for their lives at the foot of the Bundesliga. Furthermore, it seemed league experience was preferred over raw talent by coach Felix Magath, so first-team appearances proved hard to come by. Nevertheless, Koo showed the necessary determination when he was thrust into yet another relegation battle at Augsburg. With top-flight experience notably lacking at the Bavarian club, coach Jos Luhukay put his faith in Koo's creativity in their quest to stay up.
Koo accepted the responsibility gladly and, with five goals in 15 appearances, guided FCA to an unexpectedly comfortable finish to their first ever Bundesliga campaign. The creative midfielder earned a new three-year contract with Wolfsburg in the process, but returned to Augsburg on loan for the 2012/13 season. His partnership with compatriot Ji Dong Won, on loan from Sunderland AFC, played an integral role in Augsburg collecting 24 points post-Christmas to once again ensure their Bundesliga survival.
He returned to the Volkswagen Arena with a point to prove, but made just ten league appearances for Dieter Hecking's team during the first half of the campaign. Koo will now be looking to rediscover his Augsburg form at the Coface Arena. If he succeeds in doing so, der Karnevalverein will have some player on their hands, one who may be set to make a name for himself at the 2014 FIFA World Cup.