Gary Gentry's journey in Major League Baseball began when he was drafted by the New York Mets in the third round of the 1967 amateur draft. A right-handed pitcher, Gentry quickly rose through the ranks, making his MLB debut with the Mets on April 10, 1969. His rookie season proved to be a memorable one, as he played a vital role in the Mets' remarkable run to their first World Series championship.

During the 1969 season, Gentry started 35 games, posting a 13-12 record with a 3.43 ERA. His performance on the mound was instrumental in helping the Mets secure the National League East title. In the postseason, Gentry's talents shone brightly. He started Game 3 of the National League Championship Series against the Atlanta Braves, pitching brilliantly to earn the win. The Mets swept the Braves, advancing to the World Series to face the Baltimore Orioles.

In the World Series, Gentry was given the nod to start Game 3. He delivered a strong performance, pitching 6 2/3 scoreless innings and contributing offensively with a two-run double. The Mets won the game 5-0, taking a 2-1 lead in the series. New York went on to win the championship in five games, and Gentry's efforts were a crucial part of their success.

Gentry continued to be a reliable starter for the Mets over the next few seasons. In 1970, he recorded a 9-9 record with a 3.68 ERA, and in 1971, he improved to a 12-11 record with a 3.23 ERA. His ability to consistently deliver quality starts made him a valuable asset to the Mets' pitching rotation.

In November 1972, Gentry was traded to the Atlanta Braves along with Danny Frisella in exchange for Fรฉlix Millรกn and George Stone. His time with the Braves, however, was marred by injuries. Despite these setbacks, Gentry managed to post a 4-6 record with a 4.36 ERA in 1973. Unfortunately, his injuries continued to hamper his performance, and he struggled to regain his form in the following seasons.

Gentry's career with the Braves came to an end after the 1975 season. Over his seven-year MLB career, he compiled a 46-49 record with a 3.56 ERA and 615 strikeouts. While injuries ultimately shortened his time in the majors, Gentry's contributions to the Mets' 1969 World Series victory remain a highlight of his career.