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Mathematically (I think):
You can split the tie in three groups
Day 1 (two singles)
Day 2: (one doubles)
Day 3: (two single).

Assuming every match is 50/50, then for day one your odds are:
25% you will be up 2-0
50% you will be 1-1
25% you will be down 0-2

For day 2, you only have 50% of going 1-0, 50% going 0-1
Day three is the same as day 1, of course.

So, if by the end of day 1 you are down 0-2, your chances (again at random) of getting the next three matches are 50% (1-0 in doubles) times 25% (2-0 in the last two singles).
0.5*.025 = .0125

12.5% (or 1/8) chances of coming back from 0-2, if matches are at random.

If by the end of day 1, you are 1-1, then your chances of getting 2 of the next three are 2/3, 66% (if matches are at random)

It is as somebody said. A whole different scenario to be 1-2 because you split the first day matches, than 1-2 because you won the doubles.