Etuhu, on-loan from Manchester City, was given a stress test under anaesthetic on his ankle ligament injury on Friday.
Jones told the club's official website: "Ross will need a few more weeks in rehab, so we're looking at mid-October before he's back. He felt a slight twinge when he trained and it's knocked him back a couple of weeks.
"Kelvin is having a test and after that a decision will be taken on whether the ankle will be pinned or put in a cast.
"It's a bad one and we'll have to wait and see what Manchester City's specialist has to say. We hope it won't be pinned."