The only surprise in the $150,000 Florida Derby yesterday at Gulfstream Park was the manner in which Alydar was forced to win, and the way Believe It lost.

The experts believed Believe It, 27,774 fans' second choice, would open an easy, early lead, then try to withstand the 1-to-5 favorite's stretch surge. Instead, jockey Eddie Maple took hold of Believe It leaving the gate and rated him in behind Alydar.

This made Jerge Velesquez, aboard the Calumet colt, Police the Pace. Alydar took command from Judge Jay on the far turn - after six furlongs in a tepid 1:11 1/5 - only to find Maple challenging on the outside with Believe It.

On the stretch turn, Believe It briefly gained a head lead over Alydar, only to drift out slightly. Velesquez whacked Alydar twice with the whip at the top of the stretch and, coming to the eighth pole, the issue was no longer in doubt. Alydar scored by two lengths over Believe It with Dr. Valeri third in the field of seven, 7 1/2 lengths behind the runner-up.

Alydar paid $2.40 straight after completing the 1 1/8 miles of fast track in 1:47, only one-fifth of a second off the stakes and track record set by calumet's ill-fated Gen. Duke in 1957.

The victory was Calumet's sixth in the Florida Derby. The famed Lexington, Ky., racing establishment owned by Adm. and Mrs. Gene Markey is shooting for its ninth Kentucky Derby . . . and Alydar appears to be right on target for his May 6 date in Louisville.

I wasn't concerned when Believe It came to Alydar," trainer John Veltch remorked. "As slow as they'd been going early, I had to believe my horse would have something left, and he did. Jorge said Alydar won without urging in the last 30 or 40 yards."

Woody Stephens, the trainer of Believe It, was satisfied with the result.

"We decided to test him this way today, by taking our horse back," the Kentuckian said. "We'd beaten him on the front end in the Remsen last fall, but he ran past us in the Flamingo at Hialeah last month and we thought we'd try to take away from him what he likes best: a horse on the lead to run at."

Maple rated Believe It's effect yesterday "his best of the winter. Sensitive Prince was good, the day he beat us by a head (in the Fountain of Youth Stakes) but Alydar is a top horse."

Stephens agreed with his jockey.

"Alydar is a standout," the veteran trainer commented. Alydar will beat Sensitive Prince. He's perfect for Alydar, a quick horse Alydar can shoot at."

And what abour Affirmed, the champion 2-year-old over arch rival Alydar last season?

"Afirmed might now even win tomorrow (Sunday), in the Santa Anita Derby," Stephens declared.

Veitch is not about to write off Affirmed, which defeated Alydar in four of six races last year.

"Let's just say Alydar is at least 24 hours ahead of Affirmed, at this point," Veitch volunteered. "Actually, I was pleased in the way Alydar won today. It was a new experienc for him, having another horse come up to him after he was on the lead. He responded well. He should be a better colt for the experience."

Alydar will be shipped to Lexington Monday morning for the Blue Grass Stakes at Keeneland April 27. Believe It is going to New York Tuesday along with stablemate Quadratic. They will be pointed for the Wood Memorial at Aqudect April 22.

The other horses in the Florida Derby field probably are headed no-where, in terms of Triple Crown competition.

Alydar ran the last three furlongs yesterday in :35 4/5, the final eighth of a mile in :11 3/5.

"He finished better for me this time, more willingly, than he had in the Flamingo," Velasquez observed. "That other horse tried to dog it, but he couldn't. The two time I tapped Alydat it was with the stick down. This is the best 3-year-old I've ever been on."

Alydar earned $100,000, increasing his earnings to withiin $4 of a half-million - with the richest events ahead.