If that happens, Phillips wants to resume playing.
"I feel like I can play with it. I've played through pain before," Phillips said. "When I come back, I will try my best to see if I can play with it. If I can't, I will shut it down. I just told them to give me a chance to play with it first before they make a decision."
"When it comes to matters like this, doctor knows best," Reds manager Dusty Baker said.
Baker's Sunday lineup vs. the Indians was also without another indispensible player. Joey Votto, who returned Saturday night with two home runs, had to be scratched because he was bothered again by his left inner ear infection that causes dizziness.
"He was still feeling the effects a little," Baker said. "You knew it wasn't going to go away overnight. You wish it would. He's feeling better. He still has that woozy feeling."
Ramon Hernandez, the Reds' regular catcher, made his eighth start at first base. Jerry Hairston Jr. started at second base for Phillips.
Votto, who was batting a National League leading .371 entering the day, was a possibility to pinch-hit. That wasn't the case for Phillips, who was scheduled to meet with team medical director Dr. Tim Kremchek sometime Sunday morning. Phillips also wanted to talk to head trainer Mark Mann.
"Little do you know that I play with a pad on my finger because the vibration gets to my hand every once in a while," Phillips said. "I have long pad that goes up my finger under my batting glove. Hopefully [Mann] can do the same thing for my thumb."
During the eighth inning of Saturday's 7-6 loss to the Indians, a sharply lined grounder from Cleveland's Grady Sizemore was knocked down by Phillips' bare hand. He was still able to make the throw to first base to complete the out but it was far from a routine play.
"I knew something was wrong, because when I gripped the ball, I couldn't throw it with my fingers," Phillips said. "I just threw a palm ball to first and my finger started bleeding real bad. I tried to bend it and it wouldn't bend."
In 40 games this season, Phillips is batting .275 with seven home runs and a team-leading 34 RBIs. He's been sizzling in May, batting .350 (28-for-80) for the month.