I don't want to be negative but the challenge is not with his fitness. He will be more fit, and he is more fit right now than the 1:52 reflects - in fact - I would be he could time trial 1:48 right now - the problem is that he simply has not truly competed well in a race in two years, and he didn't again over the weekend. Some may disagree but he has always been able to time trial well - not surprising given his immense talent.
Last year, I winced when I saw him training on the Reston trails. Head down almost always, not really enjoying his craft. I saw the same body language in the race over the weekend, particularly in the first 400m.
I don't wish to write him off in any way. But it strikes me a spectacular talent should find a way to enjoy racing a a way to express his talent - and that just doesn't appear to be the case. And until he does enjoy it and mixes it up, I think it a tough row for him.