The Argentinian is expected in England on Friday for a medical ahead of becoming Alan Irvine's 11th signing since arriving at the Hawthorns in June.
Irvine said on Thursday he was keen to sign one more player to complete his squad and he wants to avoid a deadline day scramble.
He said: "We have a few plates spinning at the moment. If you pin all your hopes on one player and that one goes wrong where do you turn?
"You have got to make sure there are other options. We have a preferred choice but that might not be the one which happens.
"I'm hoping all of our work will be done by Monday so I can sit back and see what unfolds.
"We lost 13 players so straight away it meant we were going to have to bring in big numbers so it was clear it was going to be a big job in terms of creating a new squad.
"We're hoping to bring in one more and I'm hoping that doesn't have to last as long as Monday.
"We're not looking to move anyone out and if we can get this last player in I will be very happy."
New signings Joleon Lescott, Georgios Samaras and Silvestre Varela are yet to play for Albion and will not make Saturday's trip to Swansea because they lack match fitness.
"Both Samaras and Varela are some distance away but Sami is going to go away with Greece and hopefully get some playing time. That would be helpful for us," added Irvine.
"Silvestre will stay here and we'll have a chance to work really hard with him so he will do a week of pre-season training and another week where he'll do partly pre-season and partly with the group."