Nils Petersen has completed a permanent transfer to Werder Bremen on a four-year contract for an undisclosed fee.
Ozkan Yildirim has signed a new contract to keep him at Werder Bremen until 2016.
PSG coach Carlo Ancelotti has revealed the club may target Real Madrid forward Cristiano Ronaldo in the future and would relish the chance to partner him with Zlatan Ibrahimovic.
The Ligue 1 outfit are now one of the world's wealthiest clubs following their take over by Qatar Investment Authority in 2011 and therefore no player would be out of their financial reach.
They have spent more €200million (£160m) in two seasons, with Sweden striker Ibrahimovic the latest marquee signing as they look to build a side capable of competing both at home and in Europe.
Ronaldo revealed last month that he was 'sad' at Real Madrid and although he would not reveal his reasons why, he denied it was due to money.
PSG were immediately linked with a swoop for the 27-year-old, though club president Sheik Al Khelaifi publicly denied they had made an approach.
However, Ancelotti admits he would like to bring the former Manchester United man to Paris and believes he would have no trouble fielding both him and Ibrahimovic in the same team.
"I don't know if it is a transfer the club could do. Ronaldo is the symbol of Real Madrid. But which coach could state he doesn't want Cristiano Ronaldo?" He told L'Equipe.
"I believe he could play with Ibra without any trouble. Anyway they have the qualities to play together. "
He added: "I don't think it could set any trouble of egos. At Milan, I had a lot of players with strong characters, and we built an amazing team."