The Riverhead baseball team was seeded No. 13 in the Class AA playoff bracket and will open the postseason Saturday at No. 10 Half Hollow Hills East.
The Blue Waves, who finished 12-8 overall this year, won four of their final five games of the season leading into the playoffs. Hills East posted a 13-7 record in League III.
The game will start at noon.
The winner advances to play either No. 7 Sachem East or No. 16 Bellport. The Blue Waves need to win twice to advance into the championship round, where League I champion Ward Melville awaits as the No. 2 seed.
The playoff format was revamped this year from the double elimination tournament of recent years. All the league champions automatically earn a spot in the championship round, which for Class AA is the quarterfinals. The five league champions will wait to see which of the other 13 teams win to take the final three spots.
The semifinals and finals are then a best-of-three series.
In Class A, Shoreham-Wading River was seeded No. 5 and will travel to No. 4 Westhampton Beach on Monday at 4 p.m. The Wildcats need a win to advance into the Class A championship round, where No. 2 John Glenn awaits. That would start a best-of-three series.
The Wildcats were just swept in a three-game series by Bayport-Blue Point to close out the regular season. Shoreham finished 11-7 in League VII and 11-8 overall. Westhampton went 16-4 in League VI.