After Cure the Blues failed so badly in the 1 1/8-mile Wood Memorial Stakes at Aqueduct Saturday, Proud Appeal inherited his role as the early favorite for the Kentucky Derby. In Thursday's Blue Grass Stakes at Keeneland, he will get his chance to show that he can run nine furlongs.

Proud Appeal has run brilliantly, winning seven of his eight career starts, many in dazzlingly fast memorable Gotham Stakes at Aqueduct, running a mile in a remarkable 1:33 3/5. He shows so much ability that a prominent Kentucky breeder bought a half-interest in him this week for $5 million.

But the colt has never run farther than a mile, never attempted to race around two turns. "I thingk he's got things in his favor," trainer Stanley Hough said today. "His athletic ability should help him to handle it all right." But Hough acknowledged that Proud Appeal's distance-running capability was still a big question mark.

The distance should prove more of an obstacle to Proud Appeal than his 11 opponents in the Blue Grass. Only one of them, Tap Shoes, is generally regarded as a legitimate Derby contender. Tap Shoes won Hialeah's Flamingo Stakes in his last start, but he beat a dismal field and didn't run particularly fast. Infact, he has scored most of his stakes victories by default.