User blog comment:Tachikaze Master/So I noticed something.../@comment-11372432-20150407090335/@comment-26069426-20150407140838

If you call Sleipnir to the center during 2.5 of the attack phase, similar to how you remove a monster during 2.5 of the attack phase, it would logically invalidate the attack as it does when the monster is targeted; the player is no longer a valid target because a monster is in the center position.

Is there an official ruling on this?