Celtics coach Doc Rivers said Allen is about "60 percent" to play Sunday after missing the past nine games with a sore right ankle.
"I don't know if I am confident or not, I don't have an answer," Rivers said. "I have no status. If (75 percent) is probable, I would probably lower that to 60 percent. How about that?"
Rivers said Allen hasn't even run on the floor in the past several days and understands he may struggle with his rhythm early in the series.
"If he's ready to play, we're going to play him," Rivers said. "Whether he has rhythm or can make shots, the game will dictate that. Our guys will dictate that. But I'd like to see him on the floor because like I said, rhythm or no rhythm if I tell Ray to stand in the corner, someone's going to stand next to him and that creates spacing for us."
Pierce left Thursday's game against the Milwaukee Bucks with a sprained left big toe, but did return and scored 12 points in six minutes. He said he will have no restrictions.
"It's doing pretty good, just got stiff on me last night," Pierce said. "I was able to come back in. It feels pretty good right now. I don't see it as being a really big concern."