The Turkish International, who signed for the Foxes in 2018, has emerged as a target for Diego Simeone as he looks to add defensive reinforcements.
Soyuncu has played only once for Leicester in the Premier League this season and has fallen behind the likes of Wout Faes and Daniel Amartey in the pecking order for Brendan Rodgers.
As a result, Simeone is keen to add the defender to his squad in what could be a cut-price deal. The 26-year-old is out of contract at the end of the season.
This could allow Atletico to negotiate a pre-contract agreement with Soyuncu next month. However, they may also look to bring the defender to the Metropolitano in January rather than wait until the summer. Leicester could be willing to accept a smaller amount in order to get some sort of return on their initial investment of €21m if they are unable to agree a new contract with the player.