Wests Cardinals feasted on an error-riddled Berkeley Eagles performance to keep their Illawarra baseball premiership hopes alive with a 8-5 victory in Saturday's elimination semi-final at Cringila Park.

Eagles scored three runs in the bottom of the seventh inning to tie the game 5-5, but Cardinals then scored three runs, all from errors in the eighth, to seal their spot in the preliminary final.

Third-placed Cards now face second-placed Dapto Chiefs, with the winner to meet reigning premiers Northern Pirates in the grand final on Saturday, September 12.

Pirates had their major semi-final against Chiefs washed out, but advanced to the grand final as minor premiers.

While Cards are only a win away from the grand final, they'll need to improve after a fumbling Eagles committed seven errors, with seven of Cards' eight runs coming off mistakes.

In the crucial eighth inning with the game locked 5-5, Cards' lead-off batter Scott Sartori reached base on an error and advanced to second base with Joel Thompson hitting into a fielder's choice.

Nathan Grogan was walked and Trent D'Antonio then flied out for the second out of the inning.

Eagles then committed back-to-back errors with Jeremy Bec and Josh Dean at the plate, leading to Cards scoring three runs and taking a match-winning 8-5 lead.

Sartori was Cards' top hitter with 2-4 and 2RBIs, while Josh Dean (2/5) had a double and drove in a run.

Chad Blanch went 3-4 for Eagles with 2RBIs as Berkeley outhit Cardinals 13-8, but were let down by their seven errors compared to two Cards errors.

Cards starting pitcher Mick Talty improved on a nervous first inning in which he gave up two walks and two hit-batters to throw four innings for only four hits, with one earned run.

Sartori pitched in relief and gave up nine hits and four earned runs in five innings, with five strikeouts.

Eagles starting pitcher Josh Doyle was solid, throwing six innings for seven hits with only one of his five runs earned.

Chad Blanch gave up only one hit in two innings of relief and the three runs scored off Blanch in the eighth all came from errors.

The best three teams - Pirates, Chiefs and Cards - are now left to battle for the premiership over the next fortnight.

In second grade, third-placed Chiefs beat fourth-placed Eagles 6-2 in the elimination semi-final and take on Pirates in the preliminary final on Saturday.

Second grade minor premiers Cardinals are in the grand final after their major semi against Pirates was washed out.

In third grade, Eagles (third) beat fourth-placed Mariners 10-4 and will face Cardinals in the preliminary final.

Minor premiers Pirates are in the grand final.

A decision on the venues for the preliminary finals is due early this week.