The senior, who leads the Orange in scoring, rebounding and blocks, was the catalyst of a key second-half sequence in the Carrier Dome.
With Syracuse up 39-33 and 16:28 remaining, Louisiana Tech's Erik McCree grabbed a rebound and tried to lead a fast break. But Christmas was waiting on the other end, and sent McCree's floater attempt sailing the other way down the court.
As both the Bulldogs' Leo Edwards and the Orange's Kaleb Joseph tried to track it down, Edwards picked up a foul, sending possession back to Syracuse.
The Orange are looking to snap a two-game losing streak and entered Sunday 5-3 on the season, while Louisiana Tech entered at 7-2.