Jones, who was Baltimore's lone All-Star this season, injured the ankle in a close play at first base in Tuesday's 9-6 loss to the Yankees.
"I couldn't tell you when or if he'll come back," said manager Dave Trembley. "[There was] much improvement today as far as the swelling going down, but I would say now it's probably at least a two-to-three-week period where he's not going to play. It could be longer, based upon the amount of improvement he does or does not make."
Jones sustained the injury in a strange play at first base in the sixth inning on Tuesday, a hustle play that saw him run past the base and step on the edge of it trying to get back. He appeared to hyperextend his knee, but the diagnosis was a severe sprain.
The 24-year-old had an X-ray on Tuesday night and met the media while wearing a walking boot and using crutches on Wednesday, and he said it was hard to tell if the swelling had subsided at all. His initial feeling is that he'll be able to play again this season, but he allowed that he hasn't seen the team doctor yet.
"It's a tough injury," Jones said. "I see myself playing. It's just a matter of when. It's a joint, you really can't determine when. ... It's an injury that you can't control. When you're playing, everything is going so fast, you never know what could happen. It's just unfortunate, but I have to deal with it."
Jones has also dealt with a balky hamstring and back spasms this season, and last year he missed a month with a broken bone in his left foot. This injury comes less than a week after he returned from the back ailment.
The Orioles will likely use Felix Pie in center field for the majority of games down the stretch and will fill the gap in left field with a combination of Luke Scott and Nolan Reimold. Jones may well be tougher to replace in the batting order, where he ranked second in home runs (19), runs (83) and RBIs (70) for the club.
"It's not a pleasant feeling to lose a guy the caliber of Jones," said Trembley. "There's no one who has made as much improvement from one year to the next as Jones. I think everybody can attest to that. When you lose a guy like that in the middle of the lineup, the middle of the diamond, the middle of your clubhouse, that's a major blow."
Both Trembley and Jones insist that the latter won't return until he's close to 100 percent physically. Jones said that the injury really bothers him because it will keep him from getting a chance to finish the season on a strong note. He batted .303 with 12 homers before the All-Star break and .222 with seven after it.
Still, he said that his second season has been one of growth and progress.
"My goals ... coming into this year [were] to have a better year than I did last year," he said. "And I think the first half surely indicates it. The second half, not so much. But I think overall I've grown as a player, and I feel there's so much more I need to learn. It was a good season for me. It was a success, although it's not ending the way I would hope."
Trembley said that the one bright side he can take from the situation is that Pie has played better of late and will get a chance to continue his own hot streak. Trembley also said that the team doesn't plan on making any further roster moves and that Scott, Reimold and Jeff Fiorentino will handle left-field duties the rest of the way.
That situation will require a little finesse, because Scott has been auditioning at first base in recent days and the Orioles are trying to ease Reimold off the field due to a lingering Achilles tendon ailment.
"I could start playing Scott out there in left field a little bit, because Reimold's condition is also a concern of mine," said Trembley. "I think we've said all along that I'd DH him to get him off his feet a little bit, so Scott might find some time out there in left field. Fiorentino becomes a valuable commodity because he can play all three."
Spencer Fordin is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.