Bill Meltzer has a good write up on the MacDonald waiving. But here is why it was him and not others:
http://www.hockeybuzz.com/blog/Bill...Cap-Straights-Even-Without-MacDonald/45/71448
Had the Flyers elected to waive Brandon
Manning rather than MacDonald, the team would have gained $625,000 of cap space before Laughton's deal was figured in and wound up with just $345,000 --
not even enough to call up a player making the NHL minimum of $575,000 -- in the case of a non-LTIR injury.
So why waive MacDonald rather than Schenn? Two reasons: 1) With
MacDonald making $5 million and having five seasons (including 2015-16) left on his deal, he is quite
unlikely to be claimed, leaving him available for recall if and when the Flyers need him and have sufficient cap space; 2)
Schenn, making $3.6 million with an expiring contract at the end of the season, stood at least a
50-50 chance of being claimed off waivers. While a waiver claim would take his entire cap hit off the books immediately,
the Flyers would prefer to trade him to losing him for no return. Other teams with potential interest in Schenn, conversely, had no incentive to trade for him if there was a possibility of claiming him off of waivers instead.