Winning back-to-back baseball championships in the highly competitive Joe Hartmann Diamond Classic is a rarity, but that's Seneca High's mission this year.

The 34th annual Diamond Classic field was announced yesterday, and it includes defending champion Seneca, along with powerhouses such as Cherokee, Buena, Sacred Heart and Bishop Eustace.

Since the tourney started in 1974, just three schools have won at least two straight titles: Cherokee (1981-82), Gloucester Catholic (1996-98 and again in 2000-01) and Sterling (2002-03).

This year's 16-team field, which tournament director Hartmann calls "the Tournament of Champions of South Jersey," features most of the region's league/division leaders, along with seven at-large teams.

The first round starts Saturday at Maple Shade, Deptford, Overbrook and Washington Township. The quarterfinals will be held May 19 at Deptford and Washington Township, with games at 10:30 a.m. and 1:30 p.m.

The semifinals will take place on May 20 at Deptford and Washington Township at 1 p.m., followed by the 6 p.m. final at Campbell's Field in Camden, home of the Camden Riversharks.

Here are Saturday's first-round matchups:

At Maple Shade: Northern Burlington vs. West Deptford, 10:30 a.m.; St. Augustine vs. Gloucester Catholic, 1 p.m.

At Deptford: Eastern vs. Pennsville, 10:30 a.m.; Sacred Heart vs. Seneca, 1 p.m.

At Washington Township: Delsea vs. Cherokee, 10:30 a.m.; Bishop Eustace vs. Buena, 1 p.m.

At Overbrook: Winslow Twp. vs. Holy Cross, 11 a.m.; Camden Catholic vs. Egg Harbor Township, 1:30 p.m.

Pro potential. Deptford righthander Sheldon Johnson, a 6-foot-1, 185-pound senior, is drawing interest from major-league scouts and could be drafted next month.

Johnson is 4-1 with a 1.27 ERA. In 33 innings, he has struck out 48, walked only nine and allowed just 22 hits. According to Deptford coach Tim Taylor, Johnson has been throwing around 88 m.p.h. and has topped out at 91.

"He's been a starter since he was a sophomore, and he's really improved with his command," said Taylor, whose team has won six straight. "You look at his strikeout-walk ratio and that's an indication of how he's been pitching. He's getting ahead in the count and he's more of a pitcher now and not a thrower."

Johnson has defeated Highland, Williamstown, Eastern and Clearview. He will pitch again on Thursday when Deptford plays host to heavy-hitting Camden Catholic at 4 p.m.

Cutoff date. Teams with at least a .500 record on Friday's cutoff date will qualify for the single-elimination NJSIAA tournament. Pennsville (Group 1), Point Pleasant Borough (Group 2), Moorestown (Group 3), Toms River East (Group 4), Bishop Ahr (Non-Public A) and Bishop Eustace (Non-Public B) are South Jersey's defending sectional champions. Moorestown is now in the Central Jersey Group 3 section.

Cherokee back on top. After falling to No. 2 last week, Cherokee has moved back to No. 1 in The Inquirer's South Jersey rankings. The Chiefs went 3-1 during the week to replace then-No. 1 Bishop Eustace, which lost to Seneca during a 1-1 week.

Cherokee will play host to Eustace, which is now ranked No. 4, on Thursday.

Eustace has a tough week; it also faces No. 9 Seneca and No. 2 Buena during the week.

Games of the week. Here are some of this week's most intriguing matchups:

Today: Delran at Holy Cross, 3:45; Sacred Heart at Holy Spirit, 4; Eastern at Cherry Hill East, 3:45; West Deptford at Millville, 4.

Tomorrow: Cinnaminson at Bordentown, 3:45; Millville at Mainland, 4; Bishop Eustace at Seneca, 3:45.

Wednesday: Florence at Riverside, 3:45; Pennsville at Gloucester Catholic, 4; Buena at Holy Spirit, 4; West Deptford at Audubon, 3:45; Seneca at Camden Catholic, 3:45; Cherokee at Eastern, 4.

Thursday: West Deptford at Sterling, 3:45; Bishop Eustace at Cherokee, 3:45; Winslow Township at Eastern, 3:45; Camden Catholic at Deptford, 4; Buena at Shawnee, 3:45.

Friday: Holy Cross at Bordentown, 3:45; Egg Harbor Township at Mainland, 4; St. Augustine at Sacred Heart, 7; Pennsville at Pitman, 3:45; Winslow Township at Washington Township, 3:45.

Saturday: See the Joe Hartmann Diamond Classic schedule above.

Extra bases. Bordentown has won seven straight, highlighted by a 4-3 triumph over talented Northern Burlington. . . . Bishop Eustace's Dan Sieracki and Medford Tech's Zach Nelson lead South Jersey with seven homers each. . . . Cherokee first baseman Ben Flanary, who has slugged six homers, has committed to Temple. . . . .Shawnee (8-8) needs to win two of three games this week to qualify in Group 4. The Renegades face Pennsauken, Rancocas Valley and Buena, three strong opponents.

Contact staff writer Sam Carchidi

at 215-854-5181

or scarchidi@phillynews.com.