Scepovic, who is a 25-year-old striker, moved to Scottish Premiership giants Celtic from Spanish club Sporting de Gijon in the summer of 2014.
Simunovic, who is 21 years of age and plays as a central defender, has been on the books of the Bhoys since the summer of 2015 when he joined them from Croatian side Dinamo Zagreb.
“Taking £13million for Virgil van Dijk while spending £3m on Jozo Simunovic is not going to improve the team,” former Celtic winger Provan has written in The Scottish Sun.
“If Simunovic looks like he has a chance others have been a waste of money,” added the former Scotland international. “Stefan Scepovic?
"When Celtic spend two and a half million they must be sure they get value. Now on loan at Getafe, the Serb’s Celtic career is over after just a handful of starts for Deila.”
Celtic are at the top of the Scottish Premiership table at the moment with 43 points from 19 matches.
Ronny Deila’s side are level on points with Aberdeen, who are currently second in the standings on goal difference and have played two more matches.
The Bhoys are likely to win the league title in Scotland once more, but they once again disappointed in Europe this season.
Having initially failed to qualify for the group stage of the Champions League, Celtic could not progress to the knockout rounds of the Europa League.