Stuttgart director of sport Fredi Bobic has warned the players who do not pull their weight in training will find themselves out of the side.
The Swabians ended 2010 second from the bottom of the Bundesliga and table and coach Bruno Labbadia will have to revive their fortunes if they are to beat the drop.
"Only the strongest will make it," said Bobic at their training camp in Turkey.
"The players have got to work hard on their physical fitness and fully understand what Bruno Labbadia and his team are demanding.
"Something has got to happen within the team."
Stuttgart won just three league matches during the first half of the season and are already on their third coach after both Christian Gross and Jens Keller were dismissed.
Labbadia took charge of three matches before the winter break, but is only now really getting to know his players at the training camp in Belek.
"We have a tough second half of the season ahead of us and we are all going to have to pull together," Bobic added on the club's website.
"This is why we are taking a very close look at who is really up for it.
"There is a lot of quality in the team, it's just this was seldom shown in the first half of the season."
