Neither mud nor inexperience nor the ambitions of 19 other gifted and unpredictable thoroughbreds could keep yet another favorite from winning the 143rd Kentucky Derby.

Always Dreaming did not quite fit our usual image of a Derby leading man. He had never even run a stakes race before April 1 and his trainer, Todd Pletcher, was known for falling short at Churchill Downs. But as it turned out, the bettors were right. The colt's stellar performance in the Florida Derby and subsequent strong workouts signaled that he was peaking at the right time.

As always, however, the questions turn over quickly in the two weeks between the Derby and the Preakness. As good as Always Dreaming looked speeding over the slop in Louisville, he's never come back on less than a month's rest. So his stamina will be tested in a whole new way at Pimlico Race Course on May 20.

Beyond pushing against his own limitations, he'll face a solid field of new challengers and dangerous Derby holdovers.

Here are five storylines to keep an eye on as the Derby champ's next test looms:

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Is Always Dreaming a great horse or did he just have an ideal trip? 

The Derby could not have unfolded much better for the Pletcher-trained colt. He drew the No. 5 post, which allowed him to break in mild traffic while many of his top rivals banged bodies trying to dive in from the outside. Then State of Honor claimed the early lead, giving Always Dreaming a perfect target to stalk.

That said, when jockey John Velazquez asked him to go, he easily left Irish War Cry and Battle of Midway behind. And he would not let Lookin At Lee close on him with a late charge. So Always Dreaming is an impressive horse. And the way he galloped out suggested he was far from exhausted by his victory.

He has won on both fast tracks and on the mud at Churchill Downs. And he's won the two toughest races of his career rather easily.

So he at least might be a great horse. The questions will linger, however, until he wins on shorter rest, fights through a jolt from another horse or overcomes a bum post position. These are the same doubts most 3 year-olds face at this juncture. It's just that the scrutiny on the Derby winner is so much greater.

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Can Classic Empire regain his status at the top of this 3-year-old class? 

Speaking of jolts from other horses, they don't come much harder than the one Classic Empire took from McCraken during the post-break scrum in the Derby. Jockey Julien Leparoux said he was lucky to remain upright, and trainer Mark Casse said his horse never had a real chance to catch Always Dreaming after that.

But Classic Empire did fight like a demon to claim fourth place in the end. And his effort did speak to the same toughness he showed in rallying to win the Arkansas Derby. He was the morning-line favorite in the Derby for a reason. No less an authority than trainer Bob Baffert called him the best horse in the race.

So Casse gave racing fans a thrill when he said Classic Empire would take another shot at Always Dreaming in the Preakness. After a chaotic prep season, it seems these are the two most talented horses left standing in the 3-year-old class. And the idea of them going head-to-head in a less cluttered field is tantalizing.

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Could one of the late chargers from the Derby steal this race? 

Trainer Steve Asmussen said he thought Lookin At Lee was going to catch Always Dreaming in the Derby, and only the winner's great talent prevented it.

Asmussen seemed bowled over by his horse's effort. Lookin At Lee hasn't won since August, but he's faced more good competition than any other horse in the field and always tries. Though he lacks the brilliance of Always Dreaming or Classic Empire, he's one to root for if you like grinders.

Gunnevera, seventh in the Derby, is perhaps the more gifted closer. As he showed in the Fountain of Youth Stakes, he can beat a very good field if he times his big move correctly. Trainer Antonio Sano will switch riders, from Javier Castellano to Mike Smith, in hopes of nailing that formula at Pimlico.

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Are any of the fresh horses in this field serious threats? 

Always Dreaming and Classic Empire would likely have to take steps back for that to be the case. But there are several solid horses among those who did not run in the Derby.

Royal Mo missed getting into the field at Churchill Downs by only one spot, and jockey Victor Espinoza (who rode both California Chrome and American Pharoah) raved about him before the Derby. Not to mention three-time Preakness winner Gary Stevens will be aboard.

On the other hand, his latest results _ ninth in the Rebel Stakes and third in a seemingly weak Santa Anita Derby _ weren't outstanding.

Conquest Mo Money, on the other hand, ran a close second to Classic Empire in the Arkansas Derby and was also runner-up in a good Sunland Derby field.

Both horses are sons of Uncle Mo, who has emerged as one of the best sires in the sport in recent years.

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Is this the year when we fully appreciate Todd Pletcher? 

Pletcher is only 49, but he could have quit five years ago and still had a Hall of Fame resume. He's won more purse money and more Eclipse Awards for Top Trainer (seven) than anyone in history.

Despite those remarkable numbers, he's faced nagging questions about his record in the Triple Crown series (though most trainers would have killed for a Derby victory and two wins in the Belmont Stakes).

Fellow trainers have long said Pletcher is underappreciated by the casual fan, that few grasp how difficult it is just to get so many horses to the Derby year after year.

Now that Always Dreaming has given him a second Derby victory, it seems Pletcher is having his moment. He managed to settle his horse after a nervous first few days at Churchill Downs. And he has his sights on a Preakness victory that would fill another hole in his resume.