The 19-year-old defender has joined Bayer Leverkusen as the German club announced his transfer from Olympiakos in a fee of 22 million euros.
Retsos has penned a five-year deal with Bayer Leverkusen until the summer of 2022, completing a sensational deal.
Several clubs have been chasing his signature this summer but Bayer Leverkusen were very keen to sign him as they splashed the cash to acquire the Greek defender.
