Berlin: Mario Goetze, who scored the winner in the last World Cup final, and Dortmund teammate Marco Reus have been unable to force their way into the Germany squad for two upcoming World Cup warm up matches.
"In some positions we have an extremely large choice, in others not," said Loew. "That's why we need versatile players."
The only key player unavailable is goalie Manuel Neuer, who is still recovering from a foot injury.
File image of Germany's Mario Goetze. AP
"The door to the national team is not yet shut," Loew said: "There are players we are continuing to monitor and who have a chance if they convince us in the next few weeks."
Neither Reus nor Goetze has played for Germany since 2016.
Reus, who missed both the 2014 World Cup and the 2016 Euros because he was injured, has sparkled in recent weeks since returning from another long injury.
"It seemed important to us to leave him to rediscover stability and to return to the highest level without pressure," Loew said.
Goetze, meanwhile, has been inconsistent for his club and was taken off at half time on Thursday as Dortmund were knocked out of the Europa League by Salzburg.
Goalkeepers: Bernd Leno (Bayer Leverkusen), Marc-Andre ter Stegen (Barcelona/ESP), Kevin Trapp (Paris Saint Germain/FRA)
Defenders: Jerome Boateng (Bayern Munich), Matthias Ginter (Borussia Moenchengladbach), Jonas Hector (Cologne), Mats Hummels (Bayern Munich), Joshua Kimmich (Bayern Munich), Marvin Plattenhardt (Berlin), Antonio Rudiger (Chelsea/ENG), Niklas Sule (Bayern Munich)
Midfield: Julian Brandt (Bayer Leverkusen), Emre Can (Liverpool/ENG), Leon Goretzka (Schalke), Ilkay Gundogan (Manchester City/ENG), Sami Khedira (Juventus/ITA), Toni Kroos (Real Madrid/ESP), Mesut Ozil (Arsenal/ENG), Sebastian Rudy (Bayern Munich),
Forwards: Julian Draxler (PSG/FRA), Mario Gomez (Stuttgart), Thomas Mueller (Bayern Munich), Leroy Sane (Manchester City/ENG), Lars Stindl (Borussia Moenchengladbach), Sandro Wagner (Bayern Munich), Timo Werner (RB Leipzig)