Kyle Edmund stepped up in Andy Murray's absence to give Great Britain the perfect start against Kazakhstan in a decisive Davis Cup group tie in Madrid.
Assured of a quarter-final place with a victory, Britain lead 1-0 in the three-rubber tie after Edmund won 6-3 6-3 against Mikhail Kukushkin.
British number one Dan Evans will put his team in the last eight if he beats Alexander Bublik later on Thursday.
Murray has been rested as he continues his comeback from hip surgery.
If Evans loses, Britain will have another chance to win the tie through Jamie Murray and Neal Skupski in a deciding doubles rubber which follows the second singles match.