Hartley was shown a red card for swearing at the referee in the Premiership final against the same opponents last year, an indiscretion which cost him a place on the British and Irish Lions tour of Australia.
The firebrand hooker was dismissed after 17 minutes for elbowing Leicester centre Matt Smith in an off-the-ball incident.
He could face a lengthy suspension which would force him to miss all or part of England's Six Nations campaign in February and March as they build for September and October's home World Cup.
Hartley's absence did not prevent Northampton from sealing a stunning 23-19 victory over Leicester with 14 men.
(Reporting by Ed Osmond, editing by Mark Meadows)
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