Guillermo Garcia-Lopez, 29, drew in for his first Davis Cup appearance in a do-or-die match against Milos Raonic, Canada's top singles player. Canada entered play with a 2-1 lead and needed just one more win in the final two singles matches to claim the best-of-five series.
Garcia-Lopez replaced Marcel Granollers, 26, who was tagged as Spain's top singles player for this event as the five-time Davis Cup champion was missing its four top players.
Granollers, ranked 34th in the world, was upset by Frank Dancevic of Niagara Falls, Ont., ranked 166th, on Friday night. The Spaniard also played a gruelling doubles match Saturday that last almost four hours.
Canada was seeking to advance to the second round of the Davis Cup World Group for the first time. The World Group is open to the top 16 countries on the globe.
Spain had up to an hour before Sunday's first match to change its lineup.