Question about X races

[kev]

Jerry, when looking at a horse\'s line that you like and somewhere on the sheet the horse throws in a bad race. Besides the sy,my, differ surface or a dead rail, what else would you be looking for? and out of those i said are there any stronger than one or the other?? Also, the dead rail mark, could you please go into detail about that a bit??

[TGnick]

Jerry\'s swamped, and asked me to cover this.  
Horses nowadays have less excuses for x\'ing.  Change of surface (dirt/turf, as well as off tracks), change of distance, in general, going off a pattern, may produce an X that\'s excusable for one race (although, even in these cases, the change represents a trainer with fingers crossed hoping an ouchy horse will take to the change.)  The short answer is that true x\'s (more than 3 or 4 points) make the horse very suspect.  I would want that \"somewhere on the sheet\" to be as far back as possible from today\'s race.  
Dead rails represent a non-effort, an x with a legitimate excuse.  Since a horse\'s last race is generally the main factor in determining its odds next out, horse x\'ing on dead rails are good betting opportunities, all else being equal.