Gill, now a United director after standing down from his post to take up a role on UEFA's executive committee, has revealed the Chelsea option was a non-starter.
"We are not in the business of strengthening our key competitors in England," Gill told BBC Radio Five Live's Sportsweek programme.
"You have to see our response when Gabriel Heinze wanted to join Liverpool (in 2007). We went to a Premier League arbitration panel to show that we didn't commit to him moving within England for a certain sum of money.
"We wanted to keep (Rooney) in any event and not sell him overseas. You don't win football matches with money in the bank.