Murray, who underwent hip surgery in January,
won the European Open in Antwerp last month but the three-times
Grand Slam champion is the lowest-ranked singles player in the
British team at 126 behind Dan Evans (42) and Kyle Edmund (69).
"Any time you can bring Andy into the team is going to make your
team better," Smith told reporters. "He's still working his way
back to the level he wants to get to, so people have to keep the
expectations of the right level of where he's at just now.
"What he did in Antwerp was much talked about and a brilliant
step forwards but you do have to remember this is early days in
him coming back.
"We've got really good options. With Andy, with Evo (Evans),
with Kyle, guys playing a very similar level – and with Jamie
(Murray) and Neal (Skupski) we've got strong doubles options."
The revamped Davis Cup format has group stage ties with two
singles matches and one doubles match, with Britain drawn
alongside Kazakhstan and the Netherlands.
Murray, 32, eased his way back into professional tennis by
playing doubles, partnering with older brother Jamie in
Washington earlier this year.
Jamie said they would have to "wait and see" if they would pair
up again in Madrid.
"It depends on how Andy's feeling physically, what's the best
setup for the team on that day," he added.
"But Neal and I have practised all week and we're ready to play
if called upon and I hope we'll do a good job for the team."
(Reporting by Rohith Nair in Bengaluru; Editing by Peter
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