Brazilian defensive midfielder Marcelo Mattos is officially the sixth signing by Panathinaikos this summer. The former Corinthians player signed a four-year deal, the Athens club announced. The Greens have reportedly paid 3 million euros for the acquisition. Mattos is only 23 years old but has had a rich and successful career in Brazilian soccer, particularly with Corinthians, playing next to more experienced defensive midfielders such as Gustavo Nery and Javier Mascherano. In 2005, he won the Brazilian league with the Corinthians. The other five signings by Panathinaikos this summer have been Dame N’Doye, Arkadiusz Malarz, Elini Dimoutsos, Giorgos Karagounis and Orestis Karnezis. On Wednesday, Nasif Morris and Sotiris Leontiou extended their contracts until 2011.