But he suffered a horror injury while on national team duty with Colombia, in their match against Venezuela.
The right-back sustained a fractured fibula and ankle injury and could now miss six months of action.
It leaves Bayer with a shortfall at right-back and exploring their options.
Former Manchester United man Valencia would be allowed to join Bayer outside of the transfer window.
35-year-old Valencia is looking for a new club in Europe after leaving Ecuadorian side LDU Quito in July.
If Bayer follow up, Valencia could have one final hurrah in Europe before hanging up his boots.
Valencia spent a decade with Man United from 2009 until 2019, winning two Premier League titles during his stay.