Watch: MacKinnon ejected after throwing helmet at Garland
The Colorado Avalanche superstar was assessed four minutes for roughing and a 10-minute misconduct.
Tempers flared between the two clubs late in the third period as Colorado held a commanding 9-3 lead over its division rivals.
Avalanche head coach Jared Bednar isn't expecting MacKinnon to face any supplemental discipline for the incident.
"He might have to be a little lighter in the wallet. But I think that will be it," Bednar said, per The Athletic's Peter Baugh.
MacKinnon finished the night with two assists, two shots, and 14 penalty minutes.