But while he has every right to the appeal, he'll be in tough to convince Commissioner Gary Bettman that he deserves leniency, even as a first-time offender.
Bettman, who earlier this year upheld Patrick Kaleta's 10-game suspension in the first major test of the new two-step appeal process, has one overriding concern: to ensure that the league is seen as being strict and firm in cases where a head injury is sustained. Diminishing that perception in any way could expose the league to legal liability down the line.
That doesn't mean this is a pointless exercise, however. Bettman reduced a suspension to habitual offender Raffi Torres from 25 games to 21 after his infamous 2012 playoff assault on Marian Hossa. If Torres caught a break, anyone could.
But if Bettman holds the line as expected, Thornton can take his appeal one step further to an independent arbitrator. Kaleta chose not to pursue that route, but the NHLPA may "encourage" Thornton to serve as the test case for this right, which was newly acquired in the most recent CBA.