Right-back Salgado, 33, is in talks with Rovers over a surprise move after he left Real Madrid. And Allardyce has identified the player as being in the same mould as Hierro, another veteran Spanish defender who he signed on a short-term deal when manager at the Reebok Stadium.
"The funds are all gone so we lie with the squad that we've got," Allardyce said. "But I would like to add Michel Salgado to that - I think that he's an outstanding player of world-class quality."
The Blackburn boss added: "I think he will do a Fernando Hierro-type job for me, the same as Fernando did for me at Bolton. He (Salgado) came for a test and the test was okay. It just lies with the financial side now which is hopefully going to be okayed by early next week."
Rovers open their Premier League campaign at home to big-spending Manchester City, who are still determined to add Everton defender Joleon Lescott to their ranks before the transfer window closes.
City have already had offers of £15million and £18million rejected by the Goodison Park club, who insist the player is not for sale.