Davies, Canada's most dynamic player, has been recovering from a hamstring strain he sustained in early November playing for Bayern Munich.
Herdman confirmed Davies was en route to Doha after Canada scored a late penalty to beat Japan 2-1 in a friendly in Dubai.
Back at the World Cup for the first time since 1986, Canada open group play against second-ranked Belgium on Wednesday but may do so without Davies, who will be assessed when he arrives in Qatar.
"Phonzie (Davies) is en route now to join us and we'll assess him as soon as he arrives just to see if we can get him near his top speed," Herdman said. "Progressively, we'll just see how that one goes.
"Tonight we showed we've got the spirit the collectiveness to have a next-man up but we also know that there is only one Alphonso Davies and we are really keen to get him back."
After going 1-0 down to Japan in the ninth minute, Steven Vitoria and Lucas Cavallini, from the penalty spot in stoppage time, answered for Canada to send them into the World Cup on a positive note.
Japan also open their World Cup campaign on Wednesday when they meet Germany.
"It was a good performance tonight against one of the top technical teams," Herdman said. "We showed our commitment to push and try to get the goal which we did. It was a proud moment for us."
