Premiers Northern Pirates remain the team to beat in Illawarra baseball after overcoming Dapto Chiefs 8-6 in Saturday's final round, as both clubs kept their pitching ace in reserve for the major semi-final.

Pirates completed one of their best seasons with a record of 11 wins, one loss and one draw, but the Bucs and Chiefs know the real prize is winning this Saturday with a place in the grand final on offer.

Pirates sent Brad Drain to the mound in the final round, leaving their ace Brenden Lower in reserve, while Chiefs ace Mitch Simon sat out the last round, with Tyson Graham and Ash Miller sharing pitching duties.

Pirates scored four runs in the first inning but Chiefs scored four in the fifth and tied the game with a run in the top of the sixth.

Pirates went ahead with a run in the bottom of the sixth, plus scored two more in the seventh to take a match-winning 8-5 lead.

Pirates utility Brett McKenna had a clutch two-out 2RBI double in the first inning, while skipper Andrew Clifford went 2-4 with 2RBIs, and Drain was 2/3 with a double.

Drain pitched well for Pirates until the fifth, giving up three straight walks, with Chiefs slugger Ben Garvey capitalising with a two-run double to get the visitors back in the contest.

Stuart McCarthy (2/5, 2RBIs) and Ash Miller (2/4, double) led the hitting charts for Chiefs.

Drain gave up five hits and seven strikeouts in his five innings, with Pirates going with Travis Dutton (two innings, one hit) and 16-year-old Corey Rower (one innings, one hit) in relief.

But last season's Most Valuable Player, Lower, is likely to take on Chiefs ace Simon in a major semi-final head-to-head battle of arguably the two top pitchers in the competition.

In Saturday's other final-round clash, third-placed Wests Cardinals beat Shoalhaven Mariners 12-2 at Cringila Park.

Mariners improved significantly on their 30-2 loss to Pirates the previous week, and it was 2-2 after four innings before Cards scored four runs in the fifth and five in the seventh.

Cards face Berkeley Eagles in Saturday's first grade minor semi-final, with the winners playing the losers of the Pirates versus Chiefs clash.

Semi-final scheduling will be determined Monday night.