Seguí was born in
Holguín,
Cuba. In 1970 with Oakland, Seguí went 10–10 with two saves in 47 appearances (19 starts) while leading the
American League pitchers with a 2.56
ERA. Seguí holds the unique distinction of having pitched for both of Seattle's major league baseball teams, the Pilots and the Mariners, in the first game ever played by each franchise. In these contests, he earned a
hold for the Pilots in
1969, and absorbed the opening-day loss for the Mariners in
1977. His most productive season came in 1969 for the Pilots, when he posted career-highs in wins (12) and saves (6), against only 6 losses. Seguí also pitched with four teams in the
Venezuelan Winter League during 15 seasons between 1962 and 1983. He posted a 95–58 record and a 2.76 ERA in 213 games, setting a league's all-time record with 941 strikeouts, to surpass
Aurelio Monteagudo (897) and
José Bracho (748). This record is still unbeaten. He also ranks second in wins behind Bracho (109), third in
complete games (68), and is fourth both in ERA and
innings pitched (). Seguí was inducted into the
Venezuelan Baseball Hall of Fame and Museum in 2003. He also gained induction into the
Hispanic Heritage Baseball Museum Hall of Fame on August 19, 2006, in
San Francisco, California. In 2024, he was given the
Negro Leagues Beisbol Lifetime Achievement Award by the
Negro Leagues Baseball Museum. ==Personal life and death==