Schlotterbeck is considered to be amongst the most promising defensive prospects in the Bundesliga and newly rich Premier League side Newcastle tried to sign him in the January transfer window.
Freiburg, who are looking to qualify for Europe, shut the door on letting him go, but they will be more accommodating in the summer transfer window.
“It was clear to us that we would not give him up in the winter”, sporting director Jochen Saier, asked about Schlotterbeck, told Sky Deutschland.
“In the summer there is definitely a possibility.”
Newcastle could go back in for Schlotterbeck in the summer if they retain their Premier League status, but they would be set to face competition for his signature.
German giants Borussia Dortmund and Bayern Munich are both showing interest in the 22-year-old.
Schlotterbeck however has vowed to focus on Freiburg at present and admits he does not like to be at the centre of transfer speculation when the season is in full swing.
Newcastle wanted to sign two centre-backs in January, but landed only one in the shape of Dan Burn.
