San Antonio held the league 's best offense to just 18 points on 26 possessions in the opening period .
The Spurs posted a first quarter defensive - rating of 112.9 in their last three games coming into this one .
Spurs   held the league 's best offense to just 18 points on 26 possessions in the opening period .
The Spurs posted a first quarter defensive - rating of 112.9 in their last three games coming into this one .