"There are eight or nine players who have not played for a long time," admitted Löw in Nice after the draw for the 2016 European Championships.
"They have no playing rhythm and for some it is questionable whether they will come back in time. That worries me and gives me a headache."
The main concern is in Germany's defensive midfield where Sami Khedira and Bastian Schweinsteiger are Löw's first-choice.
Madrid's Khedira faces a race against time to be fit for Brazil having torn his cruciate knee ligament last November, while Bayern Munich's Schweinsteiger only started his first game for the European champions on Sunday after an ankle injury late last year, then a knee problem.
Their back up, Borussia Dortmund's Ilkay Gundogan, has not played since August after suffering from a back injury and a virus.
Löw received more bad news in the position on Sunday when Dortmund's Sven Bender was ruled out for 10 weeks with an inflamed pelvis.
Up front, both strikers Miroslav Klose and Mario Gomez have struggled with injuries this season.
Likewise at centre-back, Dortmund centre-back Mats Hummels is struggling to return from an ankle knock, his fourth injury since September.
Bayern's Holger Badstuber is only just starting to run again after twice tearing knee ligaments and having last played in December 2012, while fellow central defender Benedikt Höwedes of Schalke 04 has had three injuries in the last three months.
"At the World Cup, we need players who are in a very good rhythm," said Löw.
"I hope some of the players can take a few steps forwards in the next few weeks."
But Löw said he had no concerns about attacking midfielder Mesut Ozil, who's form has dipped recently at Arsenal and missed a crucial penalty in their 2-0 home defeat to Bayern Munich last week in the Champions League's last 16.
"Mesut didn't have a good day, but he can deal with criticism," said Löw, after Ozil was left out of Arsenal's 4-1 league win against Sunderland on Saturday. "He has already learnt to do that at Real Madrid. For us, he is a key component."
Germany open their World Cup campaign against Portugal in Salvador on June 16, then face Ghana and the USA in Group G.
Löw has friendlies against Chile in Stuttgart next month and Poland in May to fine-tune his World Cup squad before matches against Cameroon and Armenia just before the Germans jet to Brazil on June 7th.