Cuba mounted a threat against Saupold in the fourth, loading the bases with one out. But the right-hander got Carlos Benitez to hit a ground ball back to the mound, where Saupold began a 1-2-3 inning-ending double play.
Saupold was relieved in the fifth by Lachlan Wells, who surrendered a grand slam to Alfredo Despaigne, the game's decisive blow.
"We're under strict instructions [Saupold] wasn't to go over 50 pitches," said manager Jon Deeble. "We would have loved to have had him out there for another inning. That changes the game. ... He did a great job. I thought he threw the ball very, very well."
Saupold made his Major League debut for Detroit last season, appearing in six games overall. He gave up eight earned runs in 9 2/3 innings (7.45 ERA).
In 18 appearances (11 starts) for Triple-A Toledo in 2016, Saupold posted a 2.30 ERA and 1.16 WHIP.
The World Baseball Classic runs through March 22. In the U.S., games air live exclusively in English on MLB Network and on an authenticated basis via MLBNetwork.com/watch, while ESPN Deportes and WatchESPN provide the exclusive Spanish-language coverage. MLB.TV Premium subscribers in the U.S. have access to watch every tournament game live on any of the streaming service's 400-plus supported devices. The tournament is being distributed internationally across all forms of television, internet, mobile and radio in territories excluding the U.S., Puerto Rico and Japan. Get tickets for games at Marlins Park, Tokyo Dome, Estadio Charros de Jalisco in Mexico, Petco Park, as well as the Championship Round at Dodger Stadium, while complete coverage -- including schedules, video, stats and gear -- is available at WorldBaseballClassic.com.