Swansea boss Michael Laudrup says it is likely he will bring in a goalkeeper in January as Michel Vorm needs knee surgery.
Manager Jose Mourinho believes Ashley Cole will earn a contract extension at Chelsea.
The 32-year-old defender spent two years with the Spanish outfit, but saw out the latter part of last season on loan at Russian club Anzhi Makhachkala.
It was the Bosnian international's third spell in Russia, having previously played for Torpedo Moscow and Lokomotiv Moscow.
Bayer, third in last season's Bundesliga, have moved swiftly to add Spahic to their ranks.