|Is this distance more than three-feet?|
That said, back to the Lagares play.
Video analysis indicates that immediately upon fielding the batted ball, third baseman Arenado's first play is an attempt to tag baserunner Lagares; Torres correctly determined that the tag missed. Because we are not privy to a camera view looking straight down the 2B-to-3B baseline (the "high" or "low" third cam), we don't have an angle with which to conclusively judge whether a three-foot deviation from Lagares' base path occurred. We can do our best to piece together the mid-home (live broadcast) and center field camera angles, but even so, our look is inconclusive. For reasons we'll discuss below, Drake's look is much better for answering the base path deviation question.
MECHANICS: What IS conclusive, however, is that Torres signaled "safe" and Drake signaled "out." By default, with runners on first and second base (and less than two out), on an infield ball, the third base umpire has all plays going into third. Thus, it would appear 3B Umpire Torres read the play coming his way and ruled on the tag attempt: no tag = safe. 2B Umpire Drake had Ligares' run between the two bases and ruled on it: > 3-feet = out.
According to the MLB/WUA Joint Committee on Training, in regards to catch/no catch responsibilities, "A general rule of thumb is for the umpire to whom the glove is opening to take the ball." Specifically, a third base umpire will generally take any ball hit directly at the third baseman or that takes the third baseman to his right, while the second base umpire will take a ball that takes the third baseman to his left. In this fashion, the odd spin of the baseball took F5 Arenado to his left, which opened the play up for 2B Umpire Drake to call after he slid over to gain a parallel look, similar to the two-person crew's button hook technique in taking a BR into second base: the point here is that Drake moved to put himself in optimal position to observe the play.