The Tottenham striker began his career at White Hart Lane before moving to the Rs for just £60,000 in the summer of 2000.
He spent one season at Loftus Road, but relegation and a poor financial state at the club meant he was sold to Portsmouth.
Crouch is now back at Tottenham and Warnock knows the 30-year-old would have to accept reduced terms before a QPR return could transpire.
"If Crouchy wants to fit into the QPR wage structure, I'd welcome with open arms," he told the Fulham Chronicle. "But something tells me that isn't going to happen."
Crouch admits he has a soft spot for the newly-promoted side and the England international is not precluding the possibility of being a Hoop once again.
However, he admits Warnock has his work firmly cut out as the ex-Sheffield United boss looks to keep the Londoners in England's top-flight on a limited budget.
"I've got a lot of affection for the club, and loved playing down there when I was young," said the Spurs striker. "I certainly wouldn't rule out ever playing for QPR again.
"They deserved to win the Championship but with the level in the Premier League they will have to buy a few players and hope some of those players who got them up adapt quickly.
"It's so difficult because every year the teams who come up are expected to go down. Hopefully they do it. They've got good resources and can hopefully add to the squad they've got."