Can it be? Are we here already? The summer solstice may be June 21, but for race fans, the bugler’s call to the post at the Belmont Stakes is the harbinger of summer. Spring ends Saturday, about 2:25 minutes after they load seven horses into the gate for the Test of Champions, the 1 1/2 mile Belmont Stakes.

After the Preakness Stakes, in which Curlin dug in after being passed on the turn and wore down Street Sense on the stretch to win it in the last steps, his jockey Robby Albarado said that it was as if Curlin had begun the race as a 2-year-old and finished the race as a 5-year-old. The key to understanding Curlin is in that statement.

All horses mature as they age, and 3-year-olds are barely professionals. To watch them progress through the year is to watch the false talent and the prodigies get beat by the real horses. They begin this year — in prep races down in the warmer states — as green and skittish. At the Kentucky Derby they are all potential. When they get to Belmont, they are racehorses.

So when Albarado says a thing like that, you’ve got to take note. It was very recently, after all, that Albarado had an exhilarating series of rides on an incredible handicap horse, the 2003 Horse of the Year, Mineshaft. The horse was four, not five, at the time, but Albarado was up in the irons for that season to win seven of nine starts. He’s ridden lightning. In his 4-year-old season, he was like a horse of a different breed. To watch him win was intoxicating, especially in his last two races at Belmont Park, where he simply shut his competitors down.

Is that what Albarado means? Is he sitting on another Mineshaft?

Certainly Curlin began the year with a splash. He made his debut in February at Gulfstream Park and romped off to win by more than a dozen lengths. He jumped into graded stakes company immediately and next tore up the Rebel at Oaklawn. He came back in the Arkansas Derby and effortlessly won that race by 10 1/2. With only three starts in him, he entered the gate at the Kentucky Derby. Winning Graded Stakes races at Oaklawn is one thing, running in the Kentucky Derby is another animal altogether. It was tough going, but he stuck it out and rallied to make a real bid and get up on the board.

No one can remember anything similar to what he did at the Preakness. Before that race, he was an incredibly promising horse, but it looked like perhaps the heavy competition of the Derby had put his previous wins into proper perspective. But then he got passed at the Preakness on the turn — not just passed, but dominated — and seemed to decide that enough was enough. He was on a mission. Street Sense was running down the stretch, clicking off closing fractions that should win the Preakness, and Curlin caught him.

A horse like that, well, he’s the deserving favorite. But the race will not be handed to him. There’s steep competition in this short field of seven.

The only horse in the race I’m comfortable about dismissing is Slew’s Tizzy, and I’m only dismissing him because he’s going to inherit the pace Saturday. He’s won two in a row since they took off his blinkers, and he’s a good horse, but he’s going to be forced to run up front, since no one else in the race wants it. He’s not the kind of horse that can win the Belmont Stakes going gate to wire, especially not if he’s being challenged by the two who will be sitting right off of him: Hard Spun and Rags to Riches.

Hard Spun, who set the pace in the Derby and hung behind the blistering speed of the Preakness to finish third, is back in the gate. Larry Jones, his trainer, has a new tactic in mind for him. They want him less aggressive; they want more gas in the tank. In his final workout, he ran five furlongs in 1:03, that’s a full 5 2/5 seconds slower than the workout he had for the Derby, and one can expect that it will change his running style.

Rags to Riches, the filly, is simply wonderful. She’ll be just off the pace, hovering, waiting to strike. And when she strikes, she nails it. She closes on the stretch like a slamming door.

Everyone else will be trying to lope around the track in last, saving ground and energy so they have something left when it comes time to open up on the stretch.

Tiago and Imawildandcrazyguy are both fresh, coming into the race off five-week layoffs — three of the last four Belmonts have been won that way. Both horses will need a big step forward to win, but both are the kind of longshots that have taken advantage of the grueling distance to get under the wire.

CP West needs to take a step forward, but he took a step forward last out, when he finished fourth in the Preakness, and I think we can expect another improvement.

If Curlin really grew up, if Albarado wasn’t just gassing, then Curlin will run back to the form he ran in the Preakness, and there will be no stopping him. That’s what mature horses do — they run their race. That’s what Albarado meant when he said he rode out of the Preakness on a 5-year-old. With so little speed up front, and so little traffic to get in the way, Curlin may find himself cruising closer to the pace than he did in the Derby or the Preakness. But it won’t matter. If Albarado is serious, Curlin is going to meet the Test of Champions and prove himself. If he’s going to come back and run like the horse that won the Preakness — not the horse that started in it — then hold onto your seats, because he’s going to run a hole in the wind.

mwatman@nysun.com