Given three reference letters in a postdoc application, how to decide which to list as the second letter and which to list as the third? Usually institutes ask for three letters of reference for a postdoctoral position. Generically the first reference is the applicant's thesis adviser. Now my question is : does the ordering of second and third references matter? How should one choose the ordering?

For example, if an applicant is getting reference letters from a senior professor and a junior professor and he/she is quite sure that the junior prof. is going to give him/her a very strong letter. But he/she is not that sure about the strength of the other letter written by the senior prof. Who should he/she choose to be the 2nd reference?
In my experience I have never encountered a situation in which the ordering of reference letters mattered.
Usually the only distinction between the different letters is when you are required to have letters from your PhD/postdoc supervisor. These letters may carry more weight because they are from the people which can best assess you.

However my experience is from life sciences, not physics.