Liam Williams moves to full back with Kristian Phillips switching wings and Frazier Climo coming into the back three. Wales international Scott Williams pairs up with Nic Reynolds at centre with Rhys Priestland and Gareth Davies returning at half back. Rhodri Williams has to settle for a place on the bench.
"These games are a massive part of our season for players and coaches alike," said Easterby.
"They are big games, with the huge traditions that belong to them and are what we work towards and relish being a part of.
"You don't have to get players up for derbies and big traditional fixtures like these. The back-to-back nature to the derbies, with us heading back over the Loughor Bridge in little over a week's time, will add a bit of spice to things."
In the pack, Easterby calls on veteran prop Phil John to bolster the front row alongside Welsh internationals Ken Owens and Samson Lee. George Earle links up with Jake Ball at lock with Aaron Shingler returning from injury to replace the injured Josh Turnbull. Scottish international John Barclay and skipper Rob McCusker retain their places in the back row.
While the Scarlets rotate, the Ospreys keep changes to a minimum though they are without Wales internationals Ryan Bevington and Justin Tipuric. Both suffered injury problems in last Friday's win over the Cardiff Blues with Tipuric, who scored the only try against the Blues, failing to recover from a hip problem.
"It was a good win against Cardiff Blues on Friday night, an important one that gives us some momentum going into the game against the Scarlets," said Ospreys head coach Steve Tandy.
"It's been pleasing over the last couple of weeks to see the number of young Welsh players pulling on the shirt - they've done the region proud, showing the Ospreys have a bright future. Equally important though has been the role played by some of the experienced players and that is why it is so important we are able to keep these players at the region to give us leadership on and off the field and strength in depth."
In terms of experience, Tandy hardly lacks for options with Adam Jones, Richard Hibbard, skipper Alun Wyn Jones and No. 8 Ryan Jones all starting in two days' time.
"There was a big crowd and a good atmosphere in Cardiff, Boxing Day is heading towards a sell-out with another big crowd at the Liberty next week - it's fantastic for regional rugby," he added.
"It's an exciting time of traditional rivalries and history, games that supporters want to see week-in week-out, against familiar opposition.
"We're looking forward to these two games against the Scarlets. Going back-to-back against them is something new and it gives the games an extra bit of spice, as if that's needed in this derby.
"It's a great opportunity for fans to get out and support the cause, really showing what their region means to them."