Foster has been dealing with soreness early in camp but is expected to see game action within the next few days, James Fegan of The Athletic reports.
The specifics of the injury remain unclear, but it doesn't appear to be a serious concern with the 26-year-old scheduled to see game action in the near future. Foster made his big-league debut for the White Sox last season and impressed with a 2.20 ERA, 0.87 WHIP and 31:9 K:BB over 28.2 innings.