Warburton reportedly held talks with Forest before his exit from Rangers, although he denied any link with the Championship strugglers.
John Percy himself speculates about that in his tweet, saying "Mark Warburton to follow in the summer?".
Warburton guided Brentford to promotion from League One in 2014, but the club announced that he, McParland and assistant manager David Weir would be leaving at the end of the 2014-15 season with three months of the campaign remaining.
Rangers had hoped to appoint a director of football first but that now looks unlikely.
After the appointment was confirmed in the Mirror on Friday afternoon, Rangers fans took to Twitter to mock Nottingham Forest over their new addition.
The 56-year-old worked with Warburton as Director of Football at Watford, Brentford, and Rangers and is now looking for a new challenge.
The arrival of McParland at Nottingham Forest has enhanced the probability of Warburton becoming the club's next full-time manager.