There were two Pitchers in baseball who were named Dutch Leonard.  The first was Hubert “Dutch” Leonard, who was a lefthander who had a 139-113 record with two World Series Championships with the Boston Red Sox.  The second was Emil John “Dutch” Leonard, a righthander who may not have had a World Series Ring, but had a much longer tenure and was one of the better knuckleballers in baseball history.

Leonard debuted in 1933 with the Brooklyn Dodgers, and while he had a decent 1934 (14-11, 3.28 ERA), he faltered and was back in the minors by 1936.  The minors allowed him to perfect his knuckleball, and he was back in the Majors, this time with the Washington Senators, with whom he returned in 1938.

With the Senators, Leonard secured a 20 Win season (1939) and would go to three All-Star Games.  He was in the top ten in bWAR for Pitchers and ERA four times with Washington.  The knuckleballer was also first in WHIP (1938), and twice in BB/9 (1938 & 1943) as a Senator.

As is typical with many who mastered the knuckleball, Leonard played into his 40s.  He was with Philadelphia for two years, and at the age of 40, he joined the Chicago Cubs, where he played five more seasons, including an All-Star season in 1951.

Leonard had 191 Wins against 181 Losses over his career.

Hubert "Dutch" Leonard arrived in Boston in 1913 and immediately established himself as a left-handed force. Following a stellar rookie campaign, he authored a sophomore season in 1914 that defies modern comprehension. Leonard went 19–5 and set a Major League record with a 0.96 ERA—a mark that remains the lowest in the live-ball or deadball era for any pitcher with at least 200 innings paired that microscopic ERA with league-leading marks in FIP (1.95), WHIP (0.886), and Strikeouts per 9 (7.1).

Leonard was the engine behind the 1915 and 1916 World Series titles. While the Red Sox rotation was deep, Leonard was their postseason "Closer" before the role existed. He was a collective 2–0 with a 1.00 ERA in Fall Classic play, including a brilliant performance in 1915, where he helped dismantle the Phillies. His ability to maintain a 2.13 career ERA in Boston during a stretch when he faced some of the greatest contact hitters in history marks him as a premier talent.

His story is one of peak brilliance followed by the era's typical roster churn. Before his famous feud with Ty Cobb in Detroit or his move to the Yankees, Leonard was the left-handed anchor of Fenway Park. He threw two no-hitters in a Red Sox uniform, one in 1916 and another in 1918, joining an elite tier of "hurlers who possessed the ‘swing-and-miss' stuff necessary to dominate without the help of his defense.

Leonard left Boston with a 90–64 record and 771 strikeouts. Though his tenure was shorter than some of the "Lifers" in the Lab, his concentration of excellence was so high that he was finally inducted into the Red Sox Hall of Fame in 2012.

 

A feared knuckleball pitcher (Jackie Robinson said as much), Dutch Leonard went to three All-Star Games as a Washington Senator.  For a knuckballer, Leonard had very good control, twice leading the AL in BB/9 and once and WHIP.  As a testament o his lack of walks delivered, Leonard once led the league in SO/BB, which was especially incredible considering that he was not regarded as a Pitcher who struck out many batters.

With the Senators, Leonard had a record of 118-101 with a 3.27 ERA.