As of this writing, the youngest MLB player is Tigers pitcher Rick Porcello, Born 12/27/88
the blue jays
In 2014, the youngest manager in Major League Baseball was Mike Matheny. He is not the youngest however. He is the 14th youngest ever.
In 1974, Robin Yount became the youngest everyday player in baseball. He was 18 years old when he began his career with the Milwaukee Brewers.
So far, the answer will be Rick Porcello of Detroit Tigers, he is 21 years old
Clayton Kershaw, 20 Los Angeles Dodgers born March 19, 1988
Albert (Al) Kaline, Detroit Tigers, .340 at the age of 19.
The youngest battery in the MLB would be energizer, considering that they have only been in cooperation with the league for 24 years.