Race Comment Explainer

Original comment with matches highlighted:

chased leaders, lost place 2nd, after before 6th, off after 3 out,

Matched phrases & meanings

Phrase	Meaning
Chased leaders	Running directly behind the horses in front of the field.
tailed off	A definitive statement that the horse was finished and effectively out of the race
Weakened	The horse lost speed and dropped back through the field.
Headway	The horse was moving up through the field.

Summary

Running directly behind the horses in front of the field.
A definitive statement that the horse was finished and effectively out of the race
The horse lost speed and dropped back through the field.
The horse was moving up through the field.