With just one game left one of reigning RaboDirect PRO12 defending champions Ospreys or Scarlets will extend their season beyond May 3.
Scarlets have an advantage as they currently occupy that spot and are four points ahead of Ospreys after Jones and co fell to a 35-17 loss at Glasgow last time out.
Their rivals Scarlets had no such problems as they got the better of Cardiff Blues 24-6 and front rower Jones knows Ospreys face an uphill battle to have a chance to defend their title.
"It's obviously in their hands now," said Wales and Lions prop Jones, whose Ospreys side travel to Leinster on the final day while Scarlets host Treviso.
"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."
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