"We wanted to split up Ervin and John," Scioscia said. "This will give us some length in between them."
Saunders, who is 5-1 with a 2.66 ERA, is averaging 6.8 innings through seven starts.
"It serves two purposes," Scioscia added. "Joe gets an extra day, and it separates two guys who we wouldn't want to throw an extra 10 to 12 pitches to get out of an inning."
Neither Santana nor Saunders has fared well in Texas, so that was not a factor. Santana is 3-4 with a 8.05 ERA in nine starts at Rangers Ballpark in Arlington, and Saunders is 0-3 with a 9.77 ERA in three outings.
Neither Santana, having recovered from a sprained collateral ligament in his right elbow, nor Lackey will be under specific pitch-count restraints. But both will be watched and monitored carefully.
"They're going to have enough pitches to get deep in a game," Scioscia said. "But they're certainly not going to be in the 110- to 115-pitch range this early. I'd think they'd be between 90 and 100."
Santana and Lackey each pitched a pair of Minor League rehab games to get ready, reaching the 80-pitch range in their second starts.
With the return of Santana and Lackey, right-hander Shane Loux goes to the bullpen for now, Scisocia said. But Loux, who is 2-2 with a 4.64 ERA in six outings, could be back in a starting role on the road trip that also takes the Angels to Seattle and Dodger Stadium for a three-game Interleague series with the Dodgers.
"We're not going to rule out having him going back in the rotation," Scioscia said. "Right now we need a little depth, short term, in the bullpen -- especially with Ervin and John coming back."
Loux was effective in seven relief appearances for the Angels last season, fashioning a 2.81 ERA in 16 innings.