A pair of nicely placed forehands made for Ymer's victory.
He put up an index finger as a sign of victory and then went to his bench where the national team captain Robin Söderling, who coached in each break, received.
Sweden received an early Christmas present from the Canadian Tennis Federation when world players Felix Auger-Aliassime, eleventh in the world, and Denis Shapovalov, 14, declined the Davis Cup.
171-ranked Elias Ymer turned 1-4 in the first set and then won seven straight games and the opening single against 264-ranked Steven Diaz 6-4.6-2.
In the next single, little brother Mikael Ymer will play against Vasek Posposil.
In the new format, you play three-seater and a good three matches in each team match: Two singles and a double.
The winner of the group, which also includes Kazakhstan on Saturday, is guaranteed a place in the semi-finals, which will also be played in Madrid.
Javascript is disabled
Javascript must be turned on to play video
Read more about browser support
The browser is not supported
SVT does not support playback in your browser.
We therefore recommend that you switch to a different browser.
Read more about browser support
The Davis Cup has always been special for Mikael Ymer.
Photo: Bildbyrån