Pitching fatigue is seen as a scale of 0-100, but that's misleading. That's the scale that you see, but the actual scale is more like a low of negative infinity to a high of somewhere between 120-180 or so, depending on the pitcher's durability. When it's in the negative, you only see 0. When it's above 100, you'll see 100.
As Mike said, your guys may have been completely blasted. Their (unseen) fatigue might be somewhere around -400 or -500, depending on how badly they were abused. It may take a while for them to recover back to 100 (+).