Smith claimed his fourth goal of this season's competition after coming off the bench, but it wasn't enough as Everton won 3-1.
"Chris Iwelumo has been a leader in the dressing room," Philliskirk said.
"We are a very young team and he has been a voice on the pitch. I am not a ranter and raver.
"Chris has been an integral part of the turnaround in fortunes in the last three or four weeks.
"It had crossed our mind but lately Matt has been a fantastic impact sub so we decided to go that way.
"Hindsight is a wonderful thing and I might get criticised for not starting the lad."