Ivan Marcano is expected to arrive in Athens on Saturday to complete a medical ahead of his loan move to Olympiakos.
The Spanish centre-back and parent club Rubin Kazan have agreed a loan deal with the Greek side until the end of the season.
Rubin Kazan also revealed Olympiakos will have a 3.5million euro buy-out clause as part of the deal.
This will be Marcano's second spell with the Superleague champions, having been loaned out by Villarreal during the 2011/12 season before joining Rubin Kazan in the summer.
A statement on the Russian club's official website read: "Rubin Kazan can announce the loan of 26-year-old defender Ivan Marcano to Greek club Olympiakos.
"A buy-out clause for Olympiakos is on the contract."
Marcano will be eligible to play for Olympiakos when they take on Manchester United in the last 16 of the Champions League.