When Timo Werner signed for Chelsea in the summer of 2020, he was one of the most sought-after strikers in world soccer. The German star had a breakout stint with RB Leipzig and looked ready to take his game to the next level.

Therefore, the $58.3 million The Blues forked out for him looked like a bargain. However, nothing went according to plan. Werner struggled to settle in the Premier League and he ended up watching most games from the bench.

Having failed to impress after two seasons, Werner was sold back to Leipzig for the 2022-23 campaign. Something similar happened with former Chelsea teammate Romelu Lukaku and other stars in Europe.

Romelu Lukaku

In the summer of 2021, Lukaku was in his prime and Chelsea were recently crowned in Europe. While many thought their reunion would be the best for both, it left a lot to be desired. Eventually, Lukaku went back to Inter Milan only a year later in a season-long loan with no option to buy nor obligation clause. That means that the Belgian would once again return to London once his loan spell ends in 2023...

Antoine Griezmann

Lukaku's case may have taken many by surprise, but something similar happened with Antoine Griezmann last year. After five fantastic seasons with Atletico Madrid, the Frenchman joined Barcelona for $132m in the summer of 2019. However, he never lived up to the expectations at Camp Nou and ended up returning to the Colchoneros in 2021 in a two-year loan with option to buy.

Leonardo Bonucci

The veteran defender made a shocking, $46 million move to AC Milan in 2017 after seven years with Juventus. Nevertheless, it took him only one year to realize that his place was in Turin. In 2018, the Old Lady brought Leonardo Bonucci back for $38.50m.

Mario Gotze

After a breakthrough season in which he helped Borussia Dortmund reach the 2013 UEFA Champions League final, Bayern Munich bagged $40m to acquire the services of Mario Gotze. At 21 years of age, he was one of the biggest prospects in the Bundesliga, but he struggled to perform with the Bavarians. Only three years later, Gotze returned to Dortmund for $24 million.

Mats Hummels

Mats Hummels can relate to Gotze's situation, although he went from one club to another more than once. Having emerged from Bayern's academy, Hummels joined Dortmund on loan in 2008 but the deal was made permanent the following year. Even so, the center back returned to Bayern in 2016 for $38.50m... Only to go back to Borussia Dortmund three seasons later.

Kaka

The Brazilian star rose to stardom with AC Milan, where not only he tasted Champions League glory but also won a Ballon d'Or in 2007. Consequently, he caught the eye of Real Madrid in 2009. But Kaka never performed as expected at the Santiago Bernabeu and went back to the Rossoneri as a free agent in 2013, although his second stint was not as good as his first one.