Unless the fast time is an error in data entry or whatever , then the animal ran that time.
For whatever reason it did it.
It is up to the handicapper to find good reason why it won't repeat the effort.
This mainly applies to last start good efforts.
If this massive effort was 6 months ago , then you would need substantial reason why it should suddenly repeat.

I suggest you dump poor performance outliers and not dump the good ones.
The most important decision is that when you dump lines be aware of what you are doing and why.

Pace is not something that dogs decide as would a jockey.
But races are run at a different pace , because there may be 4 really quick early animals , and this tends to break up the Field and the slower beginners have trouble winning because they need to make up a lot of ground and need to negotiate traffic as they do so.
And only minor loss of time is usually the difference between figuring , and also rans.

If you follow horses and pace , you already have a handle on whether backmarkers are likely to figure in an event.