For a first base umpire officiating a play wherein the first baseman fields a wide throw by coming off the bag—on the x-axis, so to speak, as opposed to strictly on the vertical y-—a first base umpire's positioning should usually change as well. Generally, a base umpire can take a read step (or few) in order to position-adjust and get into a location that provides the optimal keyhole angle with which to see the fielder's gloved tag of the runner.
The reason we talk about x- vs y-axis here is that if a fielder simply jumps straight up in the air to catch a high throw, there's a pretty good chance that fielder will land straight back down on first base and we'll have a tag of the base to officiate, as opposed to a definitive tag of the batter-runner.
Thus, when 1B Umpire Knight reads that Boston fielder Dalbec has jumped away from first base to catch the ball, Knight adjusts his position, knowing that the likelihood of Dalbec attempting to tag Texas batter-runner Solak is high, and the likelihood of Dalbec attempting to touch first base is low, all based on the way the play developed.
Video as follows:
Alternate Link: Knight's adjustment at first base helps find keyhold angle on swipe tag (CCS)
Video as follows:
Alternate Link: Knight's adjustment at first base helps find keyhold angle on swipe tag (CCS)
