During these 14 golden years for the club, Rehhagel transformed Werder from a small minnow into a powerhouse, dazzling spectators with powerful up-tempo play and a smothering defence.

During this spell, Werder Bremen established themselves as one of the main teams in the Bundesliga, overtaking hated rivals Hamburg as the top club in the north and sparking an intense feud with Bayern Munich.

In this period, Rehhagel produced a host of international stars, such as Rudi Völler, Karl-Heinz Riedle, Dieter Eilts, Marco Bode, Mario Basler, Hany Ramzy, Andreas Herzog and Rune Bratseth.

After 14 golden years at Werder Bremen, Rehhagel left to manage former hated rivals, Bayern Munich, before the start of the 1995–96 season.

Prior to Rehhagel's arrival, Bayern had a disappointing, but financially lucrative season in 1994–95 (a very poor sixth place in the Bundesliga, but semi-finals in the Champions League).

In the summer of 1995, Bayern spent a lot of money, buying Jürgen Klinsmann, Andreas Herzog, and others, and Rehhagel was brought in as manager to replace Giovanni Trapattoni.

His single-minded and occasionally eccentric ways did not mesh at all with Bayern, who quickly felt that Rehhagel was too rural at heart and had no clue about how to interact in the fancy environment of Munich.

Rehhagel's job was taken over by Franz Beckenbauer, who led the team to victory in the 1996 UEFA Cup final, but saw no upturn in form in the last couple of weeks in the Bundesliga, leading Bayern to finished second, as Borussia Dortmund won their second German championship in a row.

[7] In the season after the title, Rehhagel coached Kaiserslautern to the quarter-finals of the 1998–99 UEFA Champions League and a fifth-placed finish in the Bundesliga, having club captain Andreas Brehme and libero Miroslav Kadlec.

[11] In August 2001, following Vassilis Daniil's departure, Rehhagel was appointed as the new manager of Greece,[12] ahead of other candidates, such as Marco Tardelli, Nevio Scala, Vanderlei Luxemburgo, and Terry Venables, who had also been considered for the managerial post.

[13][14] As a result, he rebuilt the squad, and in October 2003, after a 1–0 win over Northern Ireland,[15] Greece qualified automatically for Euro 2004, ahead of Spain and Ukraine.

Rehhagel adopted a defensive approach in playing his Greek side, using energetic midfielders to wear down the opponents and the policy of defending in numbers to numb the opposition's attacks.

[18] After Rudi Völler resigned as Germany coach in the wake of that country's first-round exit in Euro 2004, Rehhagel was considered by many to be a strong candidate for his homeland's job.

After three other candidates removed themselves from consideration, Rehhagel received an offer to take over as Germany coach, which he officially turned down on 10 July.

At the age of 71, he also became the oldest national team manager to coach in a FIFA World Cup, surpassing Cesare Maldini's record from 2002.

[21][22] The 2021 documentary King Otto by New York-based director Christopher André Marks chronicles Rehhagel's success in Greece.

In the period of all-round, fluid defence, many have criticized this as dated and anachronistic, with Rehhagel rebutting the claims due to his success.

Examples include Mario Basler/Marco Bode playing on the wings at Bremen or Andreas Buck/Marco Reich at Kaiserslautern while (Rudi Völler, Karl-Heinz Riedle, Frank Neubarth, Olaf Marschall, and Angelos Charisteas) at the top of the formation.

He is also famous for reigniting the careers of older players, such as Manfred Burgsmüller, Mirko Votava, Olaf Marschall or Theodoros Zagorakis.

Famous players associated with Rehhagel include Klaus Allofs, Mario Basler, Marco Bode, Rune Bratseth, Manfred Burgsmüller, Theofanis Gekas, Angelos Charisteas, Traianos Dellas, Dieter Eilts, Andreas Herzog, Marian Hristov, Miroslav Klose, Olaf Marschall, Hany Ramzy, Karl-Heinz Riedle, Wynton Rufer, Thomas Schaaf, Ciriaco Sforza, Rudi Völler, Theodoros Zagorakis, Andreas Brehme and Michael Ballack.