The reigning champions are clinging on in their battle with the Scarlets for the fourth and final play-off spot.
They must beat Leinster away from home a week Friday and hope Benetton Treviso cause an upset against the Scarlets in west Wales to secure a place.
But Jones reckons the Scarlets are red-hot favourites to hold onto a top four finish.
"It's obviously in their hands now," said the Wales prop.
"Obviously we can [reach the play-offs] but we all know the way the Scarlets are playing at the moment that it is a tough game for Treviso.
"To go there and a beat the Scarlets or restrict their points... it's obviously in their hands now.
"They are the side which came out with the good wins against the Blues and Glasgow and we bottled it.
"We weren't particularly good against Glasgow, but fair play to the Scarlets they have played better than us this season."
But the Ospreys could be bolstered by a return to action of Ryan Jones following a shoulder injury.
Jones sustained the blow in the 48th minute of Wales' RBS 6 Nations victory over Scotland and he subsequently missed the title triumph against England.
But he is delighted to be back in contention before the end of the season.
"It is the realistic opportunity to get back to playing and is the one we earmarked all along," said Jones.
"We have a must-win game against Leinster in Dublin and then we have to rely on Treviso to help us out a bit down west
"We have a chance and in sport that is all you ever need.
"You see it time and time again and that is why we turn up and all watch it. Everyone loves an upset."