Both Brazilians are defensive midfielders.
Marca says at 21, Caio is the younger and less experienced of the two. Souza, meanwhile, is a more seasoned performer. The 26-year-old started his career at Vasco da Gama and has also had a stint at Grêmio, not to mention a taste of European football, as he spent the 2010-11 season at Porto.
Caio is rated at €2 million, while Souza is valued at €5 million.