[10] He was given a lifeline when his side knocked out Primeira Liga Champions Porto 4–1 on penalties after a 1–1 draw on aggregate in the UEFA Champions League, but Schalke 04 were knocked out in the next round by Barcelona 2–0 on aggregate, and the final spell for him was a humiliating 5–1 defeat at the hands of title rival Werder Bremen.

[11] On 13 April 2008, the club management of Schalke 04 released Slomka from his obligations after several weak performances of the team.

[16] In the 2010–11 Bundesliga, Slomka led Hannover to a record fourth-place finish, thus qualifying for the 2011–12 UEFA Europa League.

[17] In the play-off round, Hannover clinched a victory over Sevilla with a 2–1 win at home, followed by a 1–1 draw away (3–2) and qualified for the 2011–12 UEFA Europa League group stage.

[18] Hannover started the 2012–13 season with a 3–0 win against St Patrick's Athletic on 2 August 2012 in the Europa League third qualifying round.

[22] On 16 February 2014, it was reported that Slomka had become head coach of Hamburger SV pending the approval of the supervisory board.

[27] He didn't pick up a single point over the final five matches of the league season.

This includes losses to Hannover 96, VfL Wolfsburg, FC Augsburg, Bayern Munich, and 1.

FC Nürnberg and Eintracht Braunschweig were unable to catch Hamburg and they finished the season in 16th place,[27] which led to a relegation–promotion play–off against Greuther Fürth.

[36] On 28 May 2019, it was confirmed that Slomka had returned to Hannover 96 for the third time as manager for the upcoming 2019–20 season.