Basketball logic says it matters.
Spurs were playing terrible team defense so practice can only help. As Poetl said, they have what they have, so this team won't suddenly become a great defensive team. They could play decent defense for sure. That's the magic of team sports: strategy + tactics + practice + execution do matter.
Cavs are on a SEGABABA, FOGAFINI, after losing a tough game in Cleveland yesterday. That should matter as well, regardless how rusty Spurs could be (SAS wins the ugly game 91-84).
That being said, I'm totally taken aback by this team. I'm unable to predict what can happen tonight.