OVERLAND PARK, Kan. (AP) _ Picking the top seeds for the NCAA baseball tournament was easy.

Seeding teams two through five in the eight regionals was difficult because of parity in college baseball, Ron Maestri, chairman of the NCAA Baseball Committee, said Monday.

The quality of competition against non-conference opponents was the determining factor in most choices for the 48-team field, Maestri said, adding that the tournament might have to consider expansion to 64 teams.

Regional play begins Thursday, with the eight-team College World Series scheduled to begin May 31.

Defending champion Cal State-Fullerton, which lost 10 of its last 15 games, was made a second seed in the Midwest Regional behind Wichita State, which won 50 of 59 games this year, the most victories of any team in the tournament. Fullerton finished the season 43-14 and remained No. 1 in the latest Baseball America poll, while Wichita State was ranked sixth.

The Southeastern Conference put the most teams in the tournament with six, while the Atlantic Coast Conference got five in.

Other top seeds were Clemson (45-15) in the Atlantic Regional at Clemson; Miami (43-12) in on Central Regional at Austin, Texas; Southern California (41-14-1) in the other Central Regional at Lubbock, Texas; Florida (44-16) in the East at Gainesville; Alabama (45-17) in one southern regional at Tuscaloosa; Louisiana State (44-15) in the other southern regional at Baton Rouge; and Florida State (47-15) in the West Regional at Stanford.

Maestri said the SEC and ACC were the two toughest conferences, but emphasized that non-conference competition was a prime factor that the committee looked at.

The committee uses a rating formula called the RPI to pick the field for the double-elimination tournament. It is based, among other things, on the difficulty of the team's schedule. The RPI ratings will not be publicly released until August, well after the series in Omaha.

Maestri said the two Texas regionals, with No. 1 seeds Miami in Austin and Southern Cal in Lubbock, could be the toughest.

``Last night we spent a lot of time making sure there was a lot of parity in all the regions,'' Maestri said. ``I'm sure the regionals at Lubbock and at (Austin) Texas are going to be tough.''

Wichita State, top-seeded and at home, is a favorite to come out of the Midwest. Cal-State Fullerton's slump at the end of the year probably cost the defending champions a top seed.

``Quite obviously, they've had a great year,'' Maestri said of Wichita State. ``They have quality wins outside the conference. Their strength is there. They deserve to be there. Fullerton started 38-4, but struggled at the end quite obviously. But they are tournament tested.''

College baseball was led by pitchers this year, particularly Kris Benson of Clemson, which meets Charleston, S.C., in the first round. He led the nation with a 1.52 earned run average and was 10-0.

Tennessee, which meets West Virginia in another Atlantic Regional, has R.A. Dickey, who was 6-1 after being turned into a starter from a relief role.

Louisiana State, which plays Austin Peay in the first round, set an SEC record with 166 homers and had SEC player of the year Eddy Furniss, who batted .376 while hitting 16 homers and driving in 68 runs.

Florida State, which went through the ACC undefeated at 15-0, was sent West to Stanford because the committee did not have room geographically to keep it at home, Maestri said. J.D. Drew leads Florida State at .421 with 14 homers.

Eighteen teams earned automomatic berths by winning conference championships, and 12 other conferences held play-in competition to fill six remaining spots. The NCAA Baseball Committee filled out the field by selecting at-large teams.

Southern Cal, Florida, LSU and Florida State were in the top five behind Cal-State Fullerton in the latest Baseball America poll.

Wichita State, Clemson, South Florida (45-17), Texas Tech (47-13) and Miami rounded out the top 10.