"If this was a playoff game, he'd be playing. But we're on a stretch where it's going to be 42 [games] out of 44 [days], so we want to make sure these guys at least get a chance to recover where they can."
Without Trout in the lineup, the Angels fell to the Mariners, 11-3, in the series finale.
Entering Thursday, Trout had started all 29 of the Halos' regular-season games. He has made 28 appearances in center field and received a partial day off on April 15 by serving as the designated hitter. Scioscia said he decided to rest Trout rather than start him at DH on Thursday to avoid aggravating the hamstring.
"When it's a hamstring, it's tough to go up there and get your at-bats," Scioscia said. "There are times where you might be a little stiff and you might be able to DH to take the load off of playing a position. Mike is playing a demanding defensive position. If the ball goes in the air, he's running somewhere for it.
"There's a time when maybe you can soften that load just as a preventative tool, but I think the general rule is that when it's a lower extremity issue or something that is as sensitive to what a player needs to do to play this whole game, you want to lean towards giving him the day off."
Trout, 25, extended his hitting streak to a career-high 16 games after homering against the Mariners on Wednesday. He batted .364 with seven home runs, 18 RBIs and five stolen bases in April, earning American League Player of the Month honors.
• Right-hander Ricky Nolasco, who dealt with right calf tightness during his outing against the Mariners on Wednesday, showed improvement on Thursday, and the Angels are hopeful that he'll be able to make his next start.
"He feels better," Scioscia said. "Hopefully it was just a little blip, but we're going to continue to monitor it during the week."
• The Angels optioned right-hander Brooks Pounders to Triple-A Salt Lake to clear a spot on the roster for right-hander Alex Meyer, who started against the Mariners on Thursday. Pounders, 26, has logged a 9.82 ERA over 3 2/3 innings for the Halos this year.
• Struggling second baseman Danny Espinosa returned to the lineup on Thursday after receiving a day off on Wednesday to work on his swing. Espinosa went into Thursday's game hitless in his last 19 at-bats, dropping his batting average to .160 this season.