Race Comment Explainer

Original comment with matches highlighted:

led, headed 2nd, tracked leaders on inside, last, plugge 2 out, mistake last,

Matched phrases & meanings

Phrase	Meaning
Tracked leader	Followed closely behind the leaders.
ridden before	The jockey started urging the horse aggressively before the second-last obstacle to try and get it back into contention.
Plugged on	Kept going without showing much pace.

Summary

Followed closely behind the leaders.
The jockey started urging the horse aggressively before the second-last obstacle to try and get it back into contention.
Kept going without showing much pace.