Elliott is not accused of the assault, but of breaking and entering and failing to assist the women.
Three players were released, but Elliott is one of six who were held overnight.
A Spanish judge freed Elliott, but pressed ahead with three charges of sexual assault - against Paul Dickov, Frank Sinclair and Keith Gillespie.
Three German tourists claim the players broke into their room and sexually assaulted them.
Elliott joined United from Torquay in 1992, playing 77 times before joining Oxford in late 1993.