Lock Evans damaged his shoulder scoring a second half try in Saturday's 30-24 defeat at Cardiff Blues on Saturday, while wing Shane Williams is nursing sore ribs.
Jones said: "The Scarlets at home is the biggest game of the season for us and I want to give Ian and Shane as much time as possible to prove their fitness for the visit of our neighbours to a packed Liberty Stadium.
"We have to put the disappointment of losing to the Blues behind us, our performance was pleasing, but we were punished for too many mistakes. The Scarlets will play some positive rugby against us and we have to raise our game against them."
This is the mid table Ospreys' second game in four days after they were shocked in the Welsh Capital and a bumper crowd of 20,520 is expected at Swansea's Liberty Stadium.
The Scarlets are buoyant after their historic win at three times Heineken Cup Champions, Toulouse, ten days ago and will show their faltering neighbours no festive charity. In contrast the Ospreys have an unimpressive lost four, won four Magners/Celtic League record and Davies says his squad can ill afford to show their neighbours any charity.
Davies said: "Everyone seems to be a little bit more excited about the Ospreys, they have a squad full of international players, but we have to keep the pressure on Ulster. With a full house there it is going to be a great occasion for both sides and for Welsh rugby as a whole; it's a big challenge for us.
"We've had good wins away from home, especially after our win in Toulouse, so the boys know what to expect in these derbies and we are really looking forward it."
While the Scarlets have few injury worries, the Ospreys have a few concerns. The Wales trio of hooker Huw Bennett, out with with an ankle injury, centre Sonny Parker, nursing a groin strain, and flanker Jonathan Thomas out until at least February after dislocating his shoulder, are all unavailable.
Jones will be hoping his side produce a festive win to boost confidence before January's key Heineken Cup showdowns against Stade Francais and Sale Sharks.