Cormier submitted Johnson in the second round to run his professional record to 19-1.
The New York State Athletic Commission also suspended Johnson for 30 days, which may not matter since the 33-year-old retired after losing to Cormier.
When Cormier is eligible to return to the Octagon, a potential rematch with Jon Jones looms. As FloCombat's Duane Finley tweeted, UFC doesn't exactly have a wealth of marquee opponents for the current light heavyweight champion:
Duane Finley @DuaneFinleyMMA
Current state of UFC LHW division we'll see Jones vs. Cormier 16 by 2020.2017-4-9 16:52:54
Jones was in attendance at the KeyBank Center in Buffalo, New York, to see Cormier beat Johnson firsthand.
Jones is serving a yearlong suspension for a failed drug test prior to his bout with Cormier at UFC 200. The punishment is in effect through July 6.
"If you're in class and you get suspended, you don't get to compete," Cormier said of his rival, per Sherdog's Tristen Critchfield. "Until [Jones] gets his academics in order, he can't talk to me about a fight. When he's eligible, then we can talk about a fight."
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