They join outside half Ignacio Mieres in the squad, while back row man Leonardo Senatore is available from 1 November.
"I'm delighted to finally be here as I've been waiting for months to join up with the team. The club is amazing and the players and the staff are great," Creevy told the Warriors website. "I'm excited to get out there and play my first match for Warriors and I hope we can add something and help the team to win games."
If last weekend's draw in France - Oyonnax landed a late, late penalty to scramble a share of the points - was an improvement after five straight defeat in the Premiership, Irish prop John Andress believes success is just around the corner for Dean Ryan's team. And victory at Sixways on Saturday afternoon could be the catalyst for a major revival.
"Winning is a habit so if we can get a result in this European fixture it will build confidence when we return to the Premiership. We're going to be very familiar with Sale," said Andress.
"They've been playing very well and have looked particularly strong up front recently, so it will be a good contest. It takes time for new players and coaches to click, but we're all confident we'll come into our own soon.
"The intensity of training has increased this season and there is a completely different structure and a better environment. I'm enjoying it, but it's been disappointing with the results."