Santana is expected to have a bullpen session on Sunday, and if that goes well, he's expected to jump back into the rotation on Tuesday night against the Rockies at Angel Stadium.
Sean O'Sullivan, who was sent down after winning his Major League debut in Santana's place with seven strong innings against the Giants last Tuesday, is being held back until Monday or Tuesday with Triple-A Salt Lake in order to be ready if needed to sub for Santana again.
"That will give us time to evaluate Ervin," Scioscia said.
O'Sullivan's performance was a huge lift for the Angels, who carried a six-game winning streak -- a pair of three-game sweeps of the Padres and Giants -- into the Freeway Series.
Kelvim Escobar has not yet begun to test his right shoulder, which flared up after he went five innings and threw 92 pitches against the Tigers in Detroit on June 6.
Escobar, Scioscia said, won't be available until "next weekend at the earliest."
The veteran right-hander said he will not rush it this time after overextending himself in Detroit and also in San Diego in a preseason tuneup on April 3.
The hope is that Escobar eventually will fall comfortably into the eighth-inning role vacated by Scot Shields, who had surgery on his left knee on Tuesday and won't resume any baseball-related activities for about six months.
Along with O'Sullivan's quality work and productive starts by John Lackey and Matt Palmer, the Angels prospered in San Francisco with some quality relief from a bullpen that has taken more than its share of lumps this season.
Without much fanfare, Justin Speier has been on a nice roll with a 1.84 ERA across 14 2/3 innings in his past 14 appearances. His strikeout of Aaron Rowand with two on and two outs in the eighth inning on Wednesday put Brian Fuentes in position to ring up his AL-best 18th save with two strikeouts in a perfect ninth inning.
Fuentes, who has converted 48 of his past 53 save opportunities, was dominant in the second half last season with the Rockies with a 1.75 ERA, converting his final 17 save chances.
Lyle Spencer is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.