Left Field - Carl Yastrzemski
If you listened to an older relative, read about Red Sox history, or looked at ancient videos, there is only one player for left field. Naturally, that is Carl Yaztrzemski.
On Opening Day in 1961, it became a view of the future for Yaz. I was at the game, and a single to left was hit with a runner on second. The other team assumed Williams was still in left. Yaz charged the ball, and the runner was nailed at home.
Yaz was originally an infielder, so that came into how he played the outfield, but his brilliance went far deeper than throws. Yaz captured his first of a string of GGs in 1963, and his run prevention was well noted with 17 assists that season. Even late in his career, Yaz was good for 17 nailed in 1977.
Yaz was excellent at all aspects of outfield defense, especially his understanding of the quirks of the left-field wall. Yaz was quick to the ball down the left field line, and a slow runner had a death wish trying for a second. Going to his left was another significant run-prevention aspect of Yaz's outfield play. Defensively, the Captain was a pitcher's best friend.
Yaz was not only the best defensive left fielder I ever saw in Boston but in all of baseball. In 1967, if Boston needed a hit or a defensive stop, it was Yaz.