Ok so I been training well all since hardcore since June,. and saw amazing gains over the summer in my time trials and road races and overall regular rides in generals. Still on training plan. However Did a cyclocross event today, using my mt bike. And i was more less dead last. At start of event. I was push my HRT in high zone like my normal race pace like 180's etc.
but i was riding slower then a turtle.
Felt very weak and unable to push myself. Guys who i can normally beat without thinking about it, practically kicked my ass today.
Getting lapped by everyone .

What factors would cause this. I did show up there after a night shift though, so only on 3 hours sleep, so that could be a cause. however i have particpated before in races after getting off a night shift of working and being fully energized.

Thoughts please. Suggestions?
Is this a cause of overtraining? should i take time off the bike for some time? suggestions please? advice