Cardiff will allow long-serving Kevin McNaughton to leave this summer along with Danny Gabbidon and Nicky Maynard.
Highly-rated Atletico Madrid midfielder Saul Niguez has signed a new five-year contract.
St Etienne have strengthened their attacking options with the signings of Yohan Mollo and Mevlut Erding, subject to the players passing medicals.
Rennes striker Erding and Nancy winger Mollo watched Les Verts' 2-1 win over Bordeaux on Sunday and are set to put the finishing touches to their moves ahead of Monday's deadline.
Mollo spent the second half of last season on loan at Stade Geoffroy Guichard and will return on a temporary deal, this time with the option for a permanent move, while Erding is set to sign outright.
A statement on the club's website, asse.fr, read: "Agreements in principle have been reached with AS Nancy-Lorraine for the loan (with option to buy) of Yohan Mollo and with Stade Rennais for the transfer of Mevlut Erding.
"Present in St Etienne this Sunday, the two players must now pass their medicals before signing their contracts."
Turkey international Erding enjoyed productive spells with Sochaux and most notably Paris St Germain before joining Rennes and the 26-year-old will provide competition for Brandao and Danijel Aleksic up front.
Mollo, 24, scored four goals in 19 Ligue 1 appearances and also won the Coupe de la Ligue with the club.
St Etienne have nine points from their opening four league games this season, the joint-highest total in the division, after Romain Hamouma and Loic Perrin's goals sank Bordeaux.