On 9 June 2009, Toprak suffered from a karting accident, causing him to miss the first half of the 2009–10 season but he recovered, scoring a goal against Hamburger SV on the 65th minute.

Bayer 04 Leverkusen signed Toprak as a replacement for newly retired Sami Hyypiä for a reported transfer fee of €2 to 3 million.

On 30 September 2011, Toprak was named to the Turkey national team by coach Guus Hiddink for the upcoming UEFA Euro 2012 qualifying matches against Germany and Azerbaijan.

[10] He made his Turkish debut on 15 November against Croatia in the second leg of UEFA Euro 2012 qualifying play-offs, playing the full 90 minutes of a goalless draw at the Stadion Maksimir in Zagreb which ensured that Croatia advanced to the finals 3–0 on aggregate.

His cousin, Rahman Soyudoğru, has also played professional football, including in Germany and Turkey.

[12] On 9 June 2009, Toprak was involved in a karting accident, in which he suffered severe burns and had to be treated in a special clinic.