The 28-year-old Irishman was a last minute replacement for Matt Phillips, who was withdrawn from the starting lineup as a precaution.
"James' (injury) is the most concerning at the moment because it is in the knee area and we'll get that scanned to see what that tells us," manager Tony Pulis told the club website. (www.wba.co.uk)
"Matty reported a tight hamstring so it made no sense to risk him."
West Brom also lost Chris Brunt to an injury in the same match, the midfielder substituted just before halftime with a calf issue.
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"We're hoping Chris' problem is not so serious. It's a question of whether he's strained his calf or it's just a result of landing awkwardly," Pulis added.
West Brom, who finished 10th in the league last season, host Bournemouth in their opening game of the new campaign on Aug. 12.
(Reporting by Hardik Vyas in Bengaluru, editing by Nick Mulvenney)
