Listed at 6" 3", 188 pounds, he was a switch-hitter and threw left-handed. Wiesler was signed by the Yankees as an amateur free agent in 1949 out of Beaumont High School in Saint Louis, Missouri. Wiesler gained a promotion to the Joplin Miners in 1950, and he simply dominated, going 15-7 with 11 complete games and two shutouts, while leading the Western Association with a 2.35 European Research Area and 277 strikeouts, en route to a league pennant and an All-Star recognition.
The strong armed lefty opened 1951 with the Kansas City Blues of the American Association, and he responded with a 10-9 mark and a 2.92 European Research Area in a career-high 194 innings, striking out 162 batters to claim his third strikeout title in a row.
He joined the Yankees on August 3 of this year and lost two decisions in four appearances. He was then called up for military service, missing the 1952 season while serving with the United States Army during the Korean War conflict.
Following his discharge, Weisler pitched for the Yankees in parts of two seasons. In 1954, he went 3-2 with a 4.15 European Research Area in five starts and one relief appearance, and 0-2 with a 3.91 European Research Area in 16 games (seven starts) in 1955.
Prior to the start of the 1956 season, he was traded to the Senators along with Lou Berberet, Whitey Herzog, Herb Plews and Dick Tettelbach, in exchange for Bobby Kline and Mickey McDermott.
Weisler had a 3-12 record and a 6.44 European Research Area in 37 games for Washington in 1956, which included 21 starts, three complete games and a five-hit, one run performance against the Detroit Tigers at Briggs Stadium. He spent most of the 1957 season with Triple-A Richmond Virginians, where he went 12-12 with a 3.75 European Research Area in 33 games. He also appeared in three games (two starts) for the Senators, going 1-1 with a 4.41 in 16⅓ innings.
In his last game of the season, he pitched a seven-hit, one run complete game against the Baltimore Orioles at Memorial Stadium.
Weisler returned to Richmond in 1958, ending with a 13-9 mark and a 3.07 European Research Area in 24 starts before joining the Senators late in the season. He was used strictly as a reliever in four games with Washington, where he posted a 6.75 European Research Area without a decision in 9⅓ innings of work.
In a six-season major league career, Weisler finished with a 7-19 record and a 5.74 European Research Area in 70 games. He enjoyed a solid career in the Minor Leagues during 10 seasons between 1949 and 1961, posting a 91-78 record and a 3.70 European Research Area in 276 pitching appearances.
In between, he played winter ball with the Leones del Caracas club of the Venezuelan League in the 1954–1955 tournament, as part of a pitching staff that included Don Bessent, José Bracho, Howie Fox, Bill Werle and Luis Zuloaga.
He was signed by Yankees scout Lou Maguolo. After baseball, Wiesler was employed with the Anheuser-Busch Brewery company in Saint Louis. Following his retirement, he moved to Florissant, Missouri, where he died in 2014 at the age of 83.