Phillips left Tuesday's game against the Padres early with a strain in his left calf and didn't play Wednesday or Thursday.
Reds manager Dusty Baker said Phillips probably could have played Friday, but it was a risk the skipper wasn't willing to take.
"We had to make a decision," Baker said. "It's a situation where I had to do what I thought was best for Brandon. He's not real pleased about it because he wanted to play. With the way it's going this season, it's best I give him one more day."
Baker said Phillips, who is hitting .296 with 13 home runs and 62 RBIs this season, was available to pinch-hit late in the game if needed.
"More than likely in a two-out situation, so he doesn't really have to bust it to beat out a double play or something," Baker said of Phillips' chances of playing Friday night. "You've got to use what you think is best. It's just that I can't take a chance right now. With the improvement he's made from two days ago to yesterday and today, it's worth me waiting."
Phillips did not speak to the media before Friday's game, but Baker said his All-Star second baseman was pushing hard to return to the lineup.
"It was hell holding him off today," Baker said. "He probably won't speak to me the rest of the night. I gave him some of my wife's enchiladas to try and defuse the situation. I don't think it worked too good, but that's OK. He got a meal out of it."