Well did U accidentally have Full Pitch press on and Hard tackling on? That sucks the life out of players

Also I suspect you're using attacking so the condition drops significantly faster

If so, he hit you on the counter and you got exposed bad.

And it helped that his GK saved 3 shots

I also had the same result in Level 2 where I was stronger (starting 11), but got beat 5-0 and drew 2-2.

Thats all the explanation I can offer.