TGJB,
The most important indicator of a horse being ready to run well in the Derby is two good races (pairs and tops) in the final two preps, even if one of those races is run in February. Normandy Invasion and a good number of other horses who ran Saturday were probably running in their next-to-last prep, and so their performance in that race is really important. An off race, regardless of whether a layoff is involved or anything else, is a warning sign about the horse’s likely ability to run well in the Derby.
Some horses who don’t have the preferred pattern of only pairs and tops in the final two preps will run a good race in the Derby, but there just isn’t any evidence that it is preferable that the better performance of the two be in the final prep. In fact I can’t find a Derby winner with that pattern, but can find two who ran well in their next to last prep but went back in their final preps – Monarchos and I’ll Have Another.
In the context of NI, the other factor to consider is the overall magnitude of his 2yo top. 1¼ in November is a huge number, whether he marched forward or not, and it was run months before the other fast horses who ran in the Saturday stakes ran their slower tops. He may struggle for some time to get back to it, somewhat like Mucho Macho Man did.