Tied on 17 in the final end, Pawa edged out Sain to win 21-17.
In another upset for the Black Jack squad, Danny Delany was beaten by local bowler Raymond Hills (Avondale) 17-21.
Chris Le Lievre (Onehunga) also beat former Black Jack Shannon McIlroy (Stoke) 21-14.
Keeping up appearances for the national team, Ali Forsyth and Tony Grantham made it through to the round of 16, to be played tomorrow (Monday) at 8:00am.
Black Jack Jan Khan also came through unscathed, joining Black Jack Development Squad member Angela Boyd and her sister Mandy Boyd (New Zealand National Squad).
Another New Zealand National Squad member, Clare McCaul goes into the round of 32 tomorrow.
The defending champions were also humbled by today's matches.
Raika Gregory was ousted by Shane Gibson (Milford), 15-21, in something of a driving frenzy that at one point left just a single bowl on the rink.
Then in the afternoon Marilyn McLeod (Defending Champion) went out to Rae Hammond (Mangere), 12-21, in the first round of the women's Singles post-section play.
Following in the wake of the young men's success, Keitha Heta (Homai) also bundled out former Black Jack Jan Shirley, 21-16, rolling into the teeth of gusty, unpredictable winds.