Rumor was Aaron Judge, the Yankee's biggest star, was unvaccinated. He personally sidestepped question about vaccine status and the team had publicly said a few (two?) players on a Yankees hadn't had their shots. Before opening day there were questions about if Judge would be able to play in New York.
The whole thing ended up being a mute point, because everyone on the starting roster[1] eventually got their shots so they could travel to Canada to play the Blue Jays.