A number of readers wrote in to me following my "Interference" article pointing out that first base umpire Jeff Nelson called A-Rod safe at first after the failed tag by Bronson Arroyo in Game 7 on Wednesday night - despite A-Rod never coming close to touching first base.
Initially, I agreed with my correspondents, but I was wrong to do so. On further review, and after seeing it pointed out by Ted Turocy and Josh Reyer of SABR, I realized that in fact Nelson is giving the sign in response to the missed tag. The "safe" sign is used when a tag is missed, just as it is given in when a fly ball is trapped, for example.
Nelson wasn't calling A-Rod safe at first; he got it right. Many of us watching, not as used to the intricacies of umpire signalling as they are, got it wrong. Should there be a different sign for "not out" than for "safe"? Probably, but that's no reflection on Jeff Nelson.
