Everything’s coming up Curlin. On July 28, the stallion’s son Tenfold won the Grade 2 Jim Dandy Stakes at Saratoga, with the Curlin colt Vino Rosso a flying third in the nine-furlong race, and the next day, last year’s champion 2-year-old colt Good Magic, also by Curlin, won the G1 Haskell by three lengths as the odds-on favorite.

The results of those two races are an indication of the significance tied to Curlin, the best racehorse and best stallion son of the important Mr. Prospector horse Smart Strike. Horse of the Year in 2007 and 2008, plus a winner of the Preakness, Breeders’ Cup Classic, and Dubai World Cup, Curlin was a racehorse of very considerable importance.

One of the best racehorses of the first decade of the new century, Curlin is also clearly now one of the best stallions in the country. He is all the more important because he represents a distinct branch of Mr. Prospector, one that is both quick enough to race well at 2 but is more adept at 3 when racing at distances of a mile and up.

The only other branch of Mr. Prospector to be a serious national actor in the classic scene is the Fappiano stem through Unbridled and his sons Unbridled’s Song, Grindstone, and Empire Maker. From the latter comes the 2015 Triple Crown winner American Pharoah, who is by the Empire Maker stallion Pioneerof the Nile, also sire of 2016 champion 2-year-old colt Classic Empire.

Curlin has staked out new territory for himself with Good Magic because, although the sire has always had a few promising juveniles like his first-crop classic winner Palace Malice, Curlin’s strength obviously has been with his maturing stock that grow into their typically sizable frames and improve with distance.

Palace Malice was the first indicator of this pattern of development, and the handsome bay improved further at 4, winning four graded stakes from his five starts that season, including the G1 Metropolitan Handicap. Prior to Good Magic, 2016 Preakness winner Exaggerator was probably the best juvenile by Curlin. Winner of the Saratoga Special and Delta Jackpot, as well as second in the Breeders’ Futurity in his first season, Exaggerator improved notably at 3 to win a trio of G1 stakes: the Santa Anita Derby, Preakness, and the Haskell.

Exaggerator offers some important pedigree indicators for breeders hoping to produce speedier and more precocious stock by Curlin. The 2016 Preakness Stakes winner is out of a mare by the Seattle Slew stallion Vindication, an unbeaten 2-year-old champion and winner of the Breeders’ Cup Juvenile. His sire, Triple Crown winner Seattle Slew, was an unbeaten juvenile and divisional champion in the days before the Breeders’ Cup and then continued his unbeaten streak through the 1977 Triple Crown.

This is the male line of Bold Ruler through his son Boldnesian (Santa Anita Derby) and grandson Bold Reasoning (Jersey Derby), which includes a heritage of his speed through its effortless stride. Speed is generated either by stride or by power. The Bold Ruler line, seen in simplest terms, is a stride line, and its most famous exemplar is Secretariat, the perfect stride machine. On the other hand, the Raise a Native line is a power line and generates speed through the leverage and muscularity of its hindquarter propulsion.

The evolution of this branch of Mr. Prospector through Curlin appears to be bearing toward the stride factors that add speed. In addition to Exaggerator being out of a mare by Vindication, other Curlin stakes winners have Bold Ruler-line broodmare sires such as Tapit, Boston Harbor, and Yes It’s True.

Tenfold, for instance, is out of the Tapit mare Temptress, and the handsome bay colt looked the picture of quality in the paddock before the Jim Dandy. A scopy colt with a great length of rein, Tenfold used his stride to great effect, first pressing the pace and then taking over the lead before the three-sixteenths pole to win from early pacesetter Flameaway (Scat Daddy) and the fast-closing Vino Rosso.

One of the excellent qualities of Curlin as a sire is that he appears to be unifying the stride and power elements of his mates to produce more effective and efficiently athletic racers. And that characteristic of his stock is making Curlin one of the most sought-after sires today.

Standing for $150,000 live foal at Hill ‘n’ Dale Farm outside Lexington, Curlin is covering large books of ever-improving quality, and the effect of his substance and racing excellence should be felt for years to come.