Murray – who overcame Dutchman Tallon Griekspoor 6-7 (7-9) 6-4 7-6 (7-5) on Wednesday – was rested for Great Britain's 2-1 Group E victory over Kazakhstan on Thursday.
The tie was level at 1-1 heading into a decisive doubles rubber, with Neal Skupski and Murray's older brother Jamie coming out on top 6-1 6-4.
Smith says former world number one Murray may not feature against Group C winner Germany.
"Andy is a team player and understands what is best for the team," Smith said. "There is no awkwardness about who is going to play, who isn't going to play. It is a good, open and honest discussion. That's what we will do again.
"It might be one of the more difficult decisions I've had to make, but it is also better when you have got the quality we've got to be able to have those discussions.
"We can look at who is in the best physical condition, and look at the match-ups again, linking those factors together to do what is best for the team.
"Because we are scheduled tomorrow evening, it gives us time to see if everybody is right and how they feel."