(Third time must be lucky.)
According to Macmillan, “second-guess 1. to guess what someone is going to do or what will happen 2. American to criticize someone”
The BNC provided the examples which I think you can interpret differently having no context:
1/ The idea of trying to second guess [critisize–?] those advisers is wrong. 2\ No attempt was made to ‘second guess’ the effects of any new policies that might be adopted in future.[guess] 3\ It is a bit unfair of Opposition Members to ask Ministers to make judgments on or second guess what tribunals do.[guess or critisize–?] 4\ The people just have to trust the administrators at a certain point, rather than trying to er second guess all of their decisions.[closer to ‘guess’] 5\ I’m not going to second guess her decision, we will work with her and we will work with her government.[guess or critisize–?]
–So, will anybody differ with me, and would Americans and Britons be unanimous as to what meaning (1 or 2) was implied?

I am from the UK and I would normally assume meaning #1. In a case where an event had already happened, and meaning #1 was impossible, I would probably assume a meaning something like “critically assess or reevaluate”.