By Martyn Herman
MADRID (Reuters) - Britain's Leon Smith could be the envy of the other 17 Davis Cup captains this week with three-time Grand Slam champion Andy Murray up his sleeve as a surprise second singles player.
With Murray having undergone hip-resurfacing surgery in January in a bid to salvage his career, Smith was planning for the Madrid finals without the team's talisman.
But the 32-year-old Scot's return to top form has been faster than expected with Murray winning the European Open title in Antwerp last month.
It helped him back to 126th in the rankings, behind Britain's other two singles players in Madrid; Dan Evans who is 42nd and Kyle Edmund who is 69th.
Davis Cup rules state that singles players picked for a tie must play in order of ranking, but Smith could leave out either Evans or Edmund, allowing him the luxury of sending Murray out as his second singles player in the opening rubber against a potentially weaker opponent.
No other nation in the Spanish capital will potentially have such a high-quality 'second' singles player.
"Sometimes in some ways you'd want to flip it around depending on the matches you're up against," Smith told reporters.
"But it could be a positive."
Britain begin their campaign on Wednesday when they face the Netherlands in Group E before taking on Kazakhstan on Thursday.
If Murray, who has won 30 of 33 singles rubbers for Britain, plays against the Dutch he is likely to face 179th-ranked Tallon Griekspoor or 200th-ranked Botic Van de Zandschulp.
However, he admitted playing potentially five singles matches in five days might be a step too far.
"Five days in a row would be tough just now," Murray, who almost single-handedly won the Davis Cup for Britain in 2015, said. "I did it in Antwerp ... but it was tough."
Former world number one Murray, the twice Wimbledon and reigning Olympic champion, has been a stalwart of the team and the topspin lob he played to beat David Goffin in Ghent 2015 to seal Britain's first Davis Cup title for 79 years rates as one of the standout moments of his career.
That final was unforgettable for the frenzied atmosphere and energy of the fans -- something only sporadically evident in Madrid where 18 nations have assembled in La Caja Magica for the first edition of the revamped competition.
The reception for the new format has so far been mixed but Murray believes people wanting to "bash" the event should reserve judgment until after Sunday's conclusion.
"In tennis sometimes we are reluctant to make changes, and this is a big change. We should give it an opportunity to see how it goes."
(Reporting by Martyn Herman, editing by Pritha Sarkar)