Santana, who has been on the disabled list with a strained upper forearm, had experienced some soreness in his triceps before regaining full arm strength. He delivered 45 pitches in a tuneup on Sunday night against Minor Leaguers in Arizona to convince the Angels that he's ready to rejoin the rotation.
Matt Palmer, who is 7-1 but has struggled in recent outings, will start on Saturday night, Scioscia said.
Sean O'Sullivan, having excelled in his first three Major League starts during Santana's absence, apparently will be moved into a middle relief role unless he's returned to Triple-A Salt Lake to retain his starting stamina.
O'Sullivan is 2-0 with a 3.00 ERA, while Palmer is carrying a 5.16 ERA in 11 starts and one relief appearance.
"We're looking at Friday," Scioscia said when asked about Santana, who had a productive bullpen session on Tuesday. "We're going to see how he feels.
"Palmer's most likely going to start on Saturday." O'Sullivan? "We'll have some direction moving forward on Sean," Scioscia said.
If Santana is able to make a full recovery, the Angels will have one spot available behind the foursome of John Lackey, Jered Weaver, Joe Saunders and Santana.
Dustin Moseley and Shane Loux, both recovering from arm issues, opened the season in the rotation and could be available soon to contend for the fifth spot along with Palmer and O'Sullivan.
"When you look at your rotation, you definitely want your best out there," Scioscia said. "Matty's pitched consistently. He hasn't pitched well of late, but if he pitches the way he did his first handful of starts, he can be a big part of what we're going to do."
The Angels have used 12 starting pitchers this season, the most in the Majors. They currently have five pitchers on the DL and have had eight disabled over the course of the first half.
Despite constantly juggling the rotation, it has more than held its own, led by Weaver and Saunders. The Angels' starters held opponents to four or fewer runs in 60 of the first 75 games, with 41 quality starts -- at least six innings with three or fewer earned runs.
Lyle Spencer is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.