The 26 year old is in talks with Swansea chairman Huw Jenkins over the possibility of a move to the Premiership.
Blackpool have had a formal offer rejected and Martinez is said to be keeping tabs on a player whom he managed during his time with Swansea.
In a bid to strike up the price for Rangel, Swansea chairman Jenkins said: "We're still talking through Blackpool's offer at the moment. It hasn't been accepted or rejected, we're just discussing it.
"Myself and Brendan (Rodgers) have had a meeting with Rangel and have got his views on where he sees himself at the club and his future and we've discussed the options which are staying at the club, looking at a new proposal from us or - if we did agree a fee with Blackpool - accepting the bid.
"But I think Rangel feels at the moment because of his age and where he's at in his career having been at the club a few years, he feels there's an opportunity to take advantage of. That's obviously clear and has come over quite strongly."
"The difficulty is that until we get the right offer on the table which is suitable for us, as with any player, he remains our player and that's as simple as that.
"It's up to Blackpool if they want to pursue the likelihood of signing Angel and to keep negotiations going. They're not a million miles away, but we are still talking to the player and his representatives."