The Spanish midfielder is now playing in Mexico, with Cruz Azul.
Rangers are reportedly set to sign Mexican ace Carlos Pena.
The Portuguese coach worked with Crosas at Santos Laguna.
Crosas played under prospective Glasgow Rangers boss Caixinha, another ex-Celtic employee, in Mexico, and has advised the Portuguese about moving to Ibrox.
Pedro Caixinha remains the favourite for the Rangers job.
Celtic beat Malmo 3-2 in the first leg of their Champions League play-off on Wednesday night.
Could a club Celtic are in partnership with help develop some of the Bhoys current or future players?
Ex-Celtic midfielder Marc Crosas poked fun at Rangers after their defeat to Motherwell on Sunday.