Twenty-five years passed before Secretariat, in 1973, succeeded Citation as thoroughbred racing's ninth Triple Crown winner by capturing the Kentucky Derby, Preakness and Belmont stakes.

The wait for No. 10 is not expected to be nearly so long. Seattle Slew will be 1 to 5 Saturday to join those two great horses, and the seven 3-year-olds that won the series before them, when he opposes nine rivals over the 1 1/2 miles of the $183,800 Belmont (5 p.m., WTOP-TV-9).

If successful, Seattle Slew would be the first of the 10 to take the title while still undefeated. He is eight for eight. Never has a foe finished within less than 1 1/2 lengths of the dark brown colt.

"No one ever gets overconfident when it comes to winning the Triple Crown. Seven horses have gotten this far, then been beaten," Billy Turner said this morning shortly after Seattle Slew had blown out three furlongs in 35 4/5.

"He's worked hard, he's holding his form, and they're going to have to come and get him," Turner continued. "Our game plan stays the same. If they went to run with him, he'll accommodate them. If they want to wait and take back off the pace, his job will be even easier."

Run Dusty Run, Sanhedrin, Spirit Level and Iron Constitution form the main contention for Seattle Slew. He has beaten all of them except Spirit Level, a late-developing colt from the same Meadow Stable that sent out Secretariat.

The other five entries are longshots: Mr. Red Wing, Sir Sir, Leading Scorer and the Johnny Campo-trained entry of Hey J.P. and Make Amends.

It rained heavily here Thursday and the Belmonst racing strip continued sloppy this afternoon, which means the Belmont may be run over an off track.

Opposing trainers hope the track will be slow or muddy Saturday. Seattle Slew has never had to get his feet wet or muddy during competition. Run Dusty Run, in particular, would benefit from a sloppy, muddy or heavy surface.

Jean Cruguet again rides the favorite. The French jockey, like Turner, is confident about the outcome, going so far as to say Seattle Slew may threaten Secretariat's 2-24 record if not his 31-length margin of victory.

Chasing Seattle Slew on the odds board, in their probable order, will be:

Run Dusty Run - Second in the Derby, third in the Preakness. Trainer Smiley Adams has changed jockeys, from Darrell McHargue to Sandy Hawley. Dusty had developed a runner-up complex this season.

Spirit Level - Penny Tweedy is now Mrs. Lennart Ringquist. Her trainer is now Steve DiMauro, not Luclen Laurin. Meadow Stables' silks are still blue and white, though, and this Quadrangle colt has come along splendidly in recent weeks, defeating Sanhedrin by a head here June 1 in the Peter Pan Stakes.

Sanhedrin - Lugged in during the stretch run of the Peter Pan. This horse is from the same Darby Dan barn that had Little Current, 1974 Preakness and Belmont victor. Trainer Lou Rondinello has never confused Sanhedrin with Little Current. George Velasquez leaves Iron Constitution to ride Sanhedrin.

Iron Constitution - Angel Cordero replaces Velasquez aboard this aptly named colt. Saturday marks its seventh start in eight weeks. He has come closest of any rival to Seattle Slew, losing by 1 1/2 lengths in the Preakness.