The Spaniard is set to join Manchester United shortly, after the Blues accepted a bid of £37million from their Premier League rivals.
But the Blues are understood to have a long-term strategy, which would see them make a move for Everton’s Barkley in the summer.
One short term option being considered by Mourinho’s side is to hijack Liverpool’s move for Mohamed Salah. Failing that, the Blues may reignite their interest in Inter Milan midfielder Fredy Gaurin, who is available for around £8million after his proposed move to Juventus fell through.
But Chelsea intend to launch a big bid for Barkley in the summer, and allowing Mata to leave is likely to aid that process.
Chelsea have the maximum number of non-homegrown players over the age of 21, of which Mata is one.
The club are aware it is an issue that needs to be addressed, especially with Frank Lampard, John Terry and Ashley Cole heading towards the end of their careers.
Mourinho has targeted Southampton full back Luke Shaw as a long term replacement for Cole, and may yet launch a big money bid in the closing days of this transfer window.
Chelsea also hope their close relationship with Everton will play a part in them landing Barkley in the summer, after the Blues loaned Romelu Lukaku to the Toffees for the duration of this season.