Shadab landed awkwardly on his shoulder and his head hit the ground during their narrow loss to South Africa last week. He was replaced by Usama Mir, who also took his spot in the team for their win over Bangladesh.
It was Shadab's third concussion since September last year and although he trained at Bengaluru's M Chinnaswamy Stadium on Friday, Arthur said they will take a late call.
"The latest update is Shadab went through a preliminary test today, which you've got to do as per medical protocol," Arthur told reporters ahead of Saturday's contest.
"He came through that OK, but we're in no position yet to make a decision on him. Concussion is a really important injury, and we've got to be 100% sure before we make a decision."
Pakistan are fifth in the table below New Zealand and aiming to make a late push to secure a semi-final place and Arthur said games against the Black Caps and defending champions England next week were must-win contests.
"I'll be brutally honest, I don't think we've played to our full potential this tournament yet," Arthur said. "I thought the Bangladesh game is the first game where we actually put a complete game together.
"We batted beautifully, bowled beautifully and fielded beautifully, which in all the other games we've done one or two disciplines OK. But our other disciplines let us down.
"I'd like to say we're peaking... But we found our best game against Bangladesh and I just hope that's not too late for us."
