Cardinals made the big plays but Saints played clever small ball to pinch a 4-3 win in a tense top-of-the-table battle at Ellis Park on Saturday.
The sides were level on points at the start of the round but Saints (7-5) now hold a one-point lead over Cardinals (6-5) at the top.
With all teams battling the howling winds, the competition leaders each made strong starts.
Saints leaped to a 2-0 lead at the top of the first inning when Tim Howard cracked a two-RBI single off Grant Phillips.
But Cardinals responded immediately, first when Steve Willis tripled and was brought home by Crete Whaanga, and then when Simon Maole hit a solo home run, his third of the season.
Saints added runs in each of the third and fourth innings, with Travis McIntosh singling to score Mitchell O'Neill, and Michael O'Neill bringing in Jamie Jones.
On the mound, Saints pitcher Sam Jones kept Cardinals scoreless through four consecutive innings before Whaanga batted in Willis - who had just whacked his second triple of the game - in the sixth.
Jones walked the first batter he faced in the final inning, and the tying run got to third base. But Jones kept his cool to seal the win.
Saints blew an opportunity to extend their competition lead when they wasted a 3-0 lead in a 6-3 loss to Ellis Park Maroon (5-6).
It was looking good for Saints in the bottom of the second when McIntosh, Michael Crowley and Mark Ahlfeld scored.
But Ellis Park Maroon grabbed three runs in the third inning, the highlight a run-scoring Tyron Wall double, added two more in the sixth and a final run in the seventh.
Rookie pitcher Krizevac Tuitea impressed for Maroon by giving up just four hits through seven innings.
Cardinals tasted rare double defeat when they ended the day with a 3-1 loss to Ellis Park Gold (5-6).
Pitcher Gary Pointon starred for Gold, retiring the first 13 batters he faced and conceding just one run in seven innings.
He also hit two singles and had a walk, a run and an RBI.
Dodgers (5-6) are still at the bottom of the competition but grabbed an important win when they beat Ellis Park Gold 8-3. Dodgers pitcher Ben Watts had 12 strike-outs to take his league-leading tally for the season to 68.
Premier softball will take a break this weekend, with Otago playing at the Jefferies Cup in Christchurch.
Dunedin is hosting a lower South Island under-15 tournament at Ellis Park, with teams coming from Southland, Central Otago and Eastern Southland.
