Hughes, who is now in charge at Stoke, resigned as Cottagers boss in the summer of 2011 saying he wanted to "further my experiences". At the time he had been heavily linked with a vacancy at Aston Villa but it was QPR where he was to work next, in what proved a dire spell.
The Welshman spent just 10 months at Loftus Road, narrowly avoiding relegation in 2012 and, despite heavy investment, being sacked just 12 games into the next Premier League campaign.
Hughes, who is preparing to return to Craven Cottage with Stoke this weekend, said: "I left under something of a cloud.
"At the time I made the decision to leave because, given what I knew and what I thought was going to happen in the future, I couldn't commit to a new contract.
"I made the decision to leave but, with hindsight, it was probably the wrong decision.
"When I was there I had a few doubts over what kind of investment would be made available to strengthen the team. I interpreted that as maybe the club didn't want to keep on progressing.
"Obviously, almost immediately after I left they started investing in good players and spending some money, so I probably got that wrong."
Hughes has made an encouraging start as he bids to revive his managerial career with Stoke.
Appointed in the summer, the 49-year-old has earned plaudits for the passing style he has introduced at the Britannia Stadium, football which contrasts with the club's reputation for physical and direct play.
The past fortnight has brought setbacks, however, with defeats to Arsenal and Norwich, and Hughes wants to get back to winning ways at his old club.
He said: "I don't think I have got anything to prove there. I am looking to go back there with my team now, which is Stoke, and do well.
"We need to get back on track."