Phelps, who was called up to the Majors on June 8, has played in four games entering Wednesday, but has only collected one hit in 14 at-bats.
"It's very early to make a decision and an assessment on the kid," Acta said. "[It's his] first time in the big leagues, he's only played a few games. We have to see him more. He'll play tomorrow."
Phelps was brought up as infielders Orlando Cabrera and Jack Hannahan have struggled at the plate, hitting .242 and .228, respectively.
The 24-year-old Phelps hit .299 with seven home runs and 40 RBIs in 55 games for Triple-A Columbus. But the injection of Phelps hasn't done anything to improve the Indians' offense.
"It's going to take him a little bit of time to make an adjustment up here and to get settled, get his feet wet," Acta said. "Not everybody comes in here and goes 5-for-10 right off the bat. This is a different ballgame, and these guys realize that. There's a reason why guys are down in Triple-A and guys are up here.
"He's going to have to realize that and make the adjustment and go from there. But I can't compare him with the guy I saw in Spring Training.