The Teessiders made an enquiry about the 24-year-old striker earlier in the transfer window and, although they received no encouragement on the terms that were offered, have not given up hope.
Xisco has made just 11 senior appearances and only four starts for the Magpies since his £5.7million switch from Deportivo la Coruna at the end of the 2008 summer transfer window.
His arrival, along with that of loan signing Nacho Gonzalez, proved the final straw for then manager Kevin Keegan as his relationship with the club and in particular the recruitment division headed by Dennis Wise, reached the point of no return.
Xisco, whose only goal for the Magpies came in a 2-1 Barclays Premier League defeat by Hull on September 13 2008 - his debut - spent last season on loan at Racing Santander, and there is interest from his native country once again.
Boro are understood to be offering to pay only a proportion of his wages, which are reputed to be in excess of £50,000 a week, although they are hoping that might eventually prove attractive to Newcastle if they run out of alternatives before Monday's deadline.
Mallorca-born Xisco, who is currently in the third year of a five-year contract, has been capped by his country at Under-21 level and arrived in England with a blossoming reputation.
However, he has rarely looked like living up to that potential and has proved a peripheral figure under former boss Chris Hughton and his replacement, Alan Pardew.
Boro boss Tony Mowbray is currently in the process of trying to re-shape his squad on a desperately limited budget despite selling big earners David Wheater and Gary O'Neil to Bolton and West Ham respectively.
The Teessiders currently lie in 20th place in the npower Championship table, just four points clear of the drop zone, a far cry from the promotion charge for which they had hoped when they set out under former manager Gordon Strachan.