It's not uncommon for managers to treat fringe players (who have become such for whatever reason) rather shabbily.
Back in the day, Big Ron was known for this - he had a core croup he considered "his" lads, and didn't care too much about those who weren't part of this group.
Short-term, this approach may work - as it can strengthen the unity within the core group which the manager considers essential.
Long-term, it's obviously a shite strategy. It's pretty much designed to cause division - which is, in itself, a very bad idea.
Fergie - by contrast - preferred to get rid of players he didn't fancy for one reason or another. He didn't exclude or ignore them - as that would be...just silly from a long-term perspective (which is the perspective he always operated with).