"I've just got back in the Sunderland team and it would benefit me to stay and get myself ready for a week Saturday," said Collins.
"When I've been selected I've turned up and when I've got my chance to play I think I've given 100 per cent," he added.
"But at the end of the day the club pays my wages, that's the argument I suppose, and I feel I can get the treatment here.
"It's my ankle, it's not so much ligament damage but I do tend to struggle after games.
"I'm not the first player to pull out through injury, there was one or two on the last trip and I'm sure there'll be one or two more on this one."
Speaking of the withdrawl John Toshack said
"Danny prefers not to join us and concentrate on what he sees as more important and that is getting a regular place at Sunderland.
"I can understand why a player might not fancy spending 10 days here and then sitting on the bench, but he might even learn something watching a side as good as Germany.
"I don't know about the future, but we're trying to build something here and we can't have people popping in and out of the squad when they want."
Wales squad to play Germany on 8 September in Cardiff and Slovakia on 12 September in Trnarva:
W Hennessey (Wolves), L Price (Derby), D Coyne (Tranmere), G Bale (Spurs), J Collins (West Ham), S Evans (Wrexham), D Gabbidon (West Ham), C Morgan (Peterborough), L Nyatanga (Barnsley), S Ricketts (Hull), A Crofts (Gillingham), S Davies (Fulham), C Fletcher (Crystal Palace), M Jones (Wrexham), J Koumas (Wigan), J Ledley (Cardiff), C Llewellyn (Wrexham), C Robinson (Toronto), C Bellamy (West Ham), R Earnshaw (Derby), F Eastwood (Wolves), D Nardiello (QPR).
Germany squad:
Goalkeepers: Robert Enke (Hanover 96), Timo Hildebrand (Valencia, Spain), Jens Lehmann (Arsenal, England)
Defenders: Gonzalo Castro (Bayer Leverkusen), Arne Friedrich (Hertha Berlin), Manuel Friedrich (Bayer Leverkusen), Marcell Jansen (Bayern Munich), Philipp Lahm (Bayern Munich), Per Mertesacker (Werder Bremen), Christoph Metzelder (Real Madrid, Spain), Christian Pander (Schalke 04), Serdar Tasci (VfB Stuttgart).
Midfielders: Roberto Hilbert (VfB Stuttgart), Thomas Hitzlsperger (VfB Stuttgart), Simon Rolfes (Bayer Leverkusen), Bastian Schweinsteiger (Bayern Munich), Piotr Trochowski (Hamburg SV).
Forwards: Mario Gomez (VfB Stuttgart), Patrick Helmes (Cologne), Miroslav Klose (Bayern Munich), Kevin Kuranyi (Schalke 04), Lukas Podolski (Bayern Munich)