Matt Phillips is poised to pull out of the Scotland squad after failing to recover from a niggling hamstring injury.
Gordon Strachan is also sweating on the fitness of James Morrison, who is a doubt for West Bromwich Albion’s game against Arsenal due to an ankle problem picked up in training.
Phillips has been ruled out of Saturday's Premier League encounter at the Hawthorns and Pulis expects the winger will withdraw from Scotland's squad for the friendly against Canada and World Cup qualifier with Slovenia.
Strachan recalled Phillips for the first time after a fine season, and the 26-year-old looked set to add to his modest total of four caps earned since 2012.