Closer rating

I've always been under the impression that if a pitcher comes in the game in a save situation (9th inning or later with the lead or tying run on base or at bat) and has no closer rating, that he would immediately be fatigued. Is this not the case? Can't seem to find this covered in the rules.

He is actually treated the same as a closer 0 in my experience, as soon as a batter reaches base with a hit or BB/HBP he becomes fatigued.

The real difference is if there is anyone on the bench with a closer rating available, he will come into a closer situation over a non-closer, even if the non-closer is a much better pitcher. (generally--if your main closer is unavailable due to pitching too many games in a row--etc)