According to the player (whose name is not put on the comments in exchange for the information), Yastrzemski was not necessarily the best team guy and got along with few Red Sox teammates. He had the reputation of being a loner and did not really personalize with many of the other Boston players. In fact, on April 20, 2012, the Red Sox honored the history of their legendary stadium Fenway Park with the ballpark's 100 year anniversary. Yastrzemski, of course, was invited to attend in the festivities and did so. But according to this unnamed player, Yastrzemski entered the stadium from a different entrance than the other players and refused to interact with any of the Boston players. This was not visible from any of the media or fans, but was very evident from the generations of players who came to the event. "It wasn't that Yastrzemski thought he was better than anyone else there," the source says, "but while the older players were together to share stories and catching up, Carl did not want anything do with interacting with them." "That was the exact way he was in the locker room."
It was the way he was perceived throughout his career in Boston. He was not liked by his teammates. In fact, the only player who was chummy with Yaz was Red Sox RHP Dave Moorhead, who pitched for the Red Sox from 1963-1968. During the 1964 season, there was a lot of undermining going on with players going to management. Manager Johnny Pesky had a mentality that was more of a rah rah type and took losses very much to heart. Many players understood that you were not going to win every game and were bothered by Pesky's reaction after a loss. Yaz, while kind of staying to the beat of his own drum, went over Pesky's head to ownership and was reportedly the reason he was fired with two games to go in 1964 season. Billy Herman ran the team for the last two games as well as the 1965 and all but the last games 16 games of the 1966 season.
There is no way to say Yaz was not an all time great player in the history of the Red Sox franchise. The Hall of Famer and three time batting champ has his place in MLB history. The question I pose, if this was the case in the Boston Red Sox locker room, did the dissention among players have anything to do with the Red Sox trouble with sustaining success? Could the team had done more than the two AL Pennants in 1967 and 1975 if Yastrzemski was a better teammate? Maybe, maybe not.