Davies hasn’t played since damaging his knee in last year’s bronze medal game at the 2019 Rugby World Cup.
It will also be his first appearance in Scarlets colours in 16 months.
The match will give the wider Scarlets squad some game-time ahead of next weekend’s Guinness PRO14 opener against Munster.
The majority of the side that started the European Challenge Cup quarter-final against Toulon last weekend will sit out this game giving a number of players opportunities to stake a claim for the October 3 clash at Parc y Scarlets.
Tom Rogers starts at full-back with Ryan Conbeer and Tom Prydie featuring on the wings.
Davies partners Paul Asquith in midfield, while fly-half Sam Costelow will make his Scarlets debut following his switch from Leicester Tigers in the summer. He partners Dane Blacker at half-back.
Up front, Phil Price, Marc Jones and Werner Kruger provide plenty of front-row experience, while Josh Helps and Tevita Ratuva pack down behind them.
Jac Morgan captains the side from openside flanker and links up with Ed Kennedy and Springbok Uzair Cassiem in the back row.
The bench includes a number of the Scarlets’ rising stars, including locks Morgan Jones and Jac Price, back-rower Carwyn Tuipulotu and centre Osian Knott.
The Ospreys haven’t revealed the exact players who will be involved in their party, but will travel with an extended squad to ensure as many players as possible get game time ahead of the new season.
“This is part of our pre-season programme and a warm up for our PRO14 opener against Edinburgh. It’s an opportunity to look at players who haven’t had a chance to play,” said Toby Booth, Ospreys head coach.
Scarlets v Ospreys (Parc y Scarlets, kick-off 2pm): 15 Tom Rogers; 14 Ryan Conbeer, 13 Jonathan Davies, 12 Paul Asquith, 11 Tom Prydie; 10 Sam Costelow, 9 Dane Blacker; 1 Phil Price, 2 Marc Jones, 3 Werner Kruger, 4 Josh Helps, 5 Tevita Ratuva, 6 Ed Kennedy, 7 Jac Morgan (capt), 8 Uzair Cassiem.
Reps: Dylan Evans, Taylor Davies, Shaun Evans, Javan Sebastian, Jac Price, Morgan Jones, Dan Davis, Carwyn Tuipulotu, Tom Phillips, Joe Miles, Will Homer, Dan Jones, Angus O’Brien, Osian Knott.
