Someone on Bill Simmons' podcast (also on the call were Stein and Bucher) made an interesting parallel. Headed into Christmas Day, the Lakers were struggling and the Celtics were rolling. Now the Celtics are struggling and the Cavs are rolling at home (The Cavaliers are 18-0 at home this season). Maybe the Celtics can flip the script and knock the Cavs down a peg.
Taking the parallel another step: The Lakers had a point to prove on Christmas and wanted the game more. They were tired of hearing about how great the Celtics were and wanted payback for the Finals. Now the Celtics are reeling and one would hope that they are feeling like they have something to prove. Who better to prove it against than the Cavs?