But Six Nations stars Jonathan Davies, George North and Ken Owens are rested for tonight's fixture with next weekend in mind.
Zebre have lost all 23 of their matches this season but the Scarlets' 20-22 defeat to Treviso will serve as a reminder of the danger Italian sides can pose.
Easterby said: "It's been a very positive week back in full training at Parc y Scarlets with the boost of the international players coming back and energised by their victory in the Six Nations.
"We are now clearly focused as a group on these next five games which we have to win to retain our control on a top four finish.
"During the international window, the players who remained at Parc y Scarlets have shown real commitment and have kept us in a good position. We have to respect all the teams we play now and that includes how we approach our challenge against Zebre on Friday night."
Williams starts on the wing with Gareth Owen returning from injury at full back while Shingler combines in the back row alongside experienced colleagues Johnathan Edwards and captain Rob McCusker.
Wales international centre Scott Williams settles for a place on the bench alongside impressive Wales 20 scrum-half talent Rhodri Williams.
"Zebre may have lost a lot of games this year but have come very close to teams at nearly every point - we have to be really focused on our job in hand as players and as coaches," Easterby added.
"They will be very competitive and we will not be going out there underestimating what we need to do to get a result.
"The Italian players will be very upbeat after Italy's finish to the Six Nations.
"They're well-coached and we are going to have to be really up for this and need a strong performance to get the result we need."