In 1909, while playing for the Perseverance team, Rondeau was discovered by Jesse Burkett and signed to play with his Worcester Busters team in the New England League.[2] He played for Worcester, principally as a first baseman but also as an outfielder, in 1909 and 1910. Late in the 1910 season, after injuries to the Worcester catchers, Burkett moved Rondeau to that position.[2] In 1911, he was sold to the Providence Grays in the Eastern League. After the 1911 season, he was traded to the Jersey City Skeeters of the International League.[2] He compiled a .311 batting average in 90 games for the Skeeters.[3]
On September 16, 1912, Rondeau was drafted by the Washington Senators in the Rule 5 draft, but the Senators then sold him to the Detroit Tigers two days later for $4,000.[1][4] After watching him earn the backup catcher position during spring training, E. A. Batchelor of the Detroit Free Press described Rondeau as a "scrappy" player who regularly engaged in heated dialogue with umpires over ball and strike calls – a fighting spirit that Batchelor concluded would make Rondeau valuable to the Tigers.[5] Rondeau appeared in 36 games for the 1913 Detroit Tigers, including 12 games as the team's starting catcher and four games as the starting first baseman. He compiled a .186 batting average with the Tigers.[1] In August 1913, he suffered sun stroke and was hospitalized for several days.[2]
After his release from the hospital, he was traded by the Tigers to the Minneapolis Millers of the American Association.[2] He hit .378 for Minneapolis in 19 games at the end of the 1913 season and continued to play well for Minneapolis in 1914, appearing in 150 games with a .308 batting average and .412 on-base percentage.[3] He was converted from a catcher to an outfielder in July 1914 by Minneapolis manager Joe Cantillon.[2]
In August 1914, the Millers traded Rondeau to Washington Senators.[6] Clark Griffith of the Senators parted with four major league players in exchange for Rondeau, making him the most expensive recruit for the 1915 Senators.[2] Rondeau appeared in only 14 games with the Senators in 1915, 11 as the team's starting left fielder and the others as a pinch-hitter, as his batting average plummeted to a career low .175 against big league pitching.[1]
On May 10, 1915, after a poor performance in his tryout with the Senators, Rondeau was sold by the Senators to the Minneapolis Millers. Clark Griffith stated at the time that he had given Rondeau a fair trial.[7] He compiled a .333 batting average in 129 games for the Millers.[3]
After another strong season with Minneapolis, Rondeau returned to the Senators in 1916. He appeared in 50 games, 33 as a left fielder and 17 as a right fielder, and compiled a .222 batting average and .311 on-base percentage. He appeared in his last major league game on July 1, 1916.[1] On July 5, 1916, Rondeau was returned to the Millers.[8]
In three major league seasons, Rondeau had a .206 batting average and .311 on-base percentage in 99 games and 272 at bats. He played 59 of his major league games as an outfielder and 16 games as a catcher.[1] As of the end of the 2015 season, Rondeau is the only major league baseball player in history named "Henri".[9]
Rondeau returned in July 1916 for a third run with Minneapolis in between stints with the Washington Senators. This time, Rondeau remained with the Millers as a starting outfielder for nine more years, running through the 1924 season. He compiled a career high .382 batting average in 16 games during the 1916 season. In all, he batted over .300 seven times for the Millers: .382 in 1916, .378 in 1913, .333 in 1915 and 1920, .312 in 1923, .308 in 1914, and .302 in 1924.[3] Rondeau was one of 42 players from 1902 to 1952 to play in 10 or more seasons as a member of the American Association.[10] Minnesota manager Joe Cantillon in 1921 referred to Rondeau as "an institution" with the team.[11]
After leaving the Millers, Rondeau played one more minor league season in 1925, splitting the season between the Little Rock Travelers and the Hartford Senators.[3] On September 1, 1925, while playing for Hartford, he collapsed during the eighth inning of a game and was carried to the clubhouse by his fellow players. A doctor stated that Rondeau had suffered a heart attack.[12]
