Diouf and Kaku have now been at the club nearly a fortnight after signing from Liverpool and Ashdod respectively whilst Oakes was brought to the club earlier on this week from Derby County.
Nine first team players are representing their countries this weekend so all the squad's fitness will be tested out ahead of the United game on Saturday week.
Those players involved at the training camp in Spain are: Kevin Poole, Anthony Barness, Julio Cesar, Kevin Nolan, Bruno N'Gotty, Michael Bridges, Kevin Davies, Ivan Campo, Fernando Hierro, El-Hadji Diouf, Ricardo Vaz-Te, Blessing Kaku, Andy Oakes
Those on international duty are: Gary Speed (Wales), Stelios Giannakopoulos (Greece), Henrik Pedersen (Denmark), Jay-Jay Okocha (Nigeria), Ricardo Gardner (Jamaica), Radhi Jaidi (Tunisia), Nicky Hunt (England U21), Jussi Jaaskelainen (Finland), Tal Ben-Haim (Israel)