determining which package is 'responsible' for forcing a downgrade ?

[snowcrash+smart]

i try to keep up-to-date daily with upgrades using smart.

though, usually, upgrades are, in fact, UP-grades, on occassion, when
@ cmd line, i,

  smart> upgrade

i receive notice that, e.g.,

  Downgrading packages (53):
  ...

i doubt that suddenly ALL '53' packages are problematic, and that a
single/few dependency/ies are causing the DOWN-grade.

how do i _simply_ determine @ cmd line *which* package is the 'culprit' here?

thanks.