Alydar runs today in the $119,000 Blue Grass Stakes against eight nondescript rivals, with his possible favorite's role in the Kentucky Derby seemingly the most important aspect of the race.

The Derby will be presented May 6 at Churchill Downs in Louisville. The Blue Grass is offered here at Keeneland, a lovely course in the heart of the thoroughbred breeding country that is located only a few miles from Calumet Farm, where Alydar was foaled.

Calumet has captured eight Derbys, Forward Pass being the most recent winner, in 1968.Alydar probably will be favored to give the stable another triumph if he wins smartly today. The son of Raise A Native out of the On-And-On mare Sweet Tooth is undefeated in four starts this season, including victories over Believe It in the Flamingo Stakes at Hialeah and the Florida Derby at Gulfstream.

Alydar was not the nation's champion 2-year-old in 1977, however. That title fell to Affirmed which defeated him in four of six races. Affirmed spent the winter in California, winning four times, including the Santa Anita and Hollywood derbys.

Those successes appear to have been fashioned against softer competition than Alydar faced in Florida. Believe it, by impressively winning the Wood Memorial Saturdy at Aqueduct, strengthened Alydar's chances of being the Derby favorite. But should Alydar disappoint in any way today, Affirmed still could gain that role.

Alydar will be 1-10 in the Blue Grass, a 1 1/8 mile event.

"He has come up to this race nicely," John Veitch observed. "He doesn't need much in order to be ready for the Derby. He was pretty well set when he got here. Once around the track should be perfect."

First prize is $77,350 and the competition could hardly be easier. Chop Chop Tomahawk and Special Honor finished a distant second and third to Sensitive Prince here last week in the Calument Purse, and the undefeated Sensitive Prince figures to be the third choice in the wagering on Derby day.

Entebbe has won but one of five outings. Go Forth's claim to fame is that he shared the same plane with Affirmed from Los Angeles to Louisville Sunday. Completing the Blue Grass lineup are Raymond Earl, Five Star General, Chabua and Sunny Songster.

All starters will carry 121 pounds. The Keeneland strip was sloppy yesterday and may not be fast today although the weather forecast calls for "mostly sunny' 'skies with temperatures in the 60s.

Calumet Farm, for all its success in the Derby, rarely has employed the Blue Grass as the final preparation for the 1 1/4-mile classic. Bull Lea, eventually Calumet's great sire, won the 1938 renewal before winding up eighth to Lawrin at Churchill, Lawrin was trained by Ben Jones, who shortly thereafter took charge of the Calumet horses.

The Jones Boys, Ben and son Jimmy, captured the Derby for Calumet with Whirlaway, 1941; Pensive, 1944; Citation, 1948; Ponder, 1949; Hill Gail, 1952; Iron Liege, 1957, and Tim Tam, 1958. They tended to use the Derby Trial at Churchill as the last prep race. Only Coaltown, in 1948, and Faultless, in 1947, won the Blue Grass for the stable and both lost in Louisville - Coaltown to stablemate Citation and Faultless by two heads to Jet Pilot and Phalanx.

This does not mean that the Blue Grass lacks solid Derby credentials. In more recent years, Tomy Lee (1959), Chateaugay (1963), Dust Commander (1970), and Riva Ridge (1972) won here before taking the first successful step on the Triple Crown trail. Forward Pass ran second for Calumet in the '68 Derby but ultimately was awarded the victory on the disqualification of Dancer's Image.