Like other trainers with horses in Saturday’s Risen Star Stakes at the Fair Grounds, Mark Casse wants to see how his 3-year-old is coming along in terms of Kentucky Derby possibilities.

Casse’s horse Airoforce is the 5-2 favorite, having won three of his four starts and finishing second in the other by a neck. But Casse said he has concerns going into the race: For one, Airoforce will be going up against Mo Tom, winner of the Lecomte Stakes on Jan. 16, as well as Tom’s Ready, who was second.

“A few of these horses have an (edge) on us because they’ve got a race over the track,” he said. “(I’m concerned) that he’s matured and a better horse. You have to continue to get better. The speed figure, time you need to do in November is a lot different than what you need to do in February or March. And you really don’t know until you run whether that’s occurred or not.”

Airoforce has not raced since Nov. 28, when he ran down the leaders on a sloppy track to win the Kentucky Jockey Club Stakes at Churchill Downs by 1¾ lengths. Mo Tom, owned by GMB Racing and trained by Tom Amoss, finished third. Tom’s Ready, also a GMB horse and trained by Dallas Stewart, was eighth.

After winning at the Kentucky Downs on Sept. 5, winning the Grade II Dixiana Bourbon Stakes on Oct. 4, finishing second in the Breeders’ Cup Juvenile Turf on Oct. 30 and winning the Jockey Club, the focus with Airoforce has been training and rest.

The decision was based partly on four races in three months, partly on Airoforce’s build, Casse said.

“He’s not some big robust horse,” he said. “He’s tall and leaner, like a lanky teenager kid. We felt like we needed to give him a little break over the winter. We figured we’d rather give up a little something early on in hopes building some momentum and having him at his best in May.”

Airoforce hasn’t gained noticeable muscle definition in the time off, Casse said. And the risk is he now could be running against horses who are closer to their best.

Amoss said Mo Tom, born late as a May foal as opposed to the traditional January foal, has had “significant” progression, particularly physically, since November.

“That makes it exciting, because he’s already shown some talent for us,” Amoss said. “So we’re hoping with this development, he’ll continue to improve.”

He is the second favorite at 3-1 and has two wins in his four starts — the other being the Street Sense Stakes on Nov. 1.

In the Kentucky Jockey Club, Mo Tom came flying up the rail on that muddy track to finish third. Asked whether that was the result of a move made too late, Amoss instead said it was part of the learning curve.

“It was a great teaching lesson for him,” he said. “A lot of horses in the race, traffic throughout, crowded trip. He gained a lot of experience from that race.”

With closing speed, Mo Tom and Airoforce seem similar in ability and build. Mo Tom drew the second post position, much to Amoss’ liking.

“I think a couple of things come into play here,” Amoss said. “I think the pace has to be legitimate early. Mo Tom needs to run his race, bring his ‘A’ game. And he needs to have a clean trip, where he’s not blocked at any point.”

The horse that finished second in the Jockey Club, Mor Spirit, is not in the Risen Star. But Gun Runner, trained by Steve Asmussen, finished fourth. Gun Runner had won his other two races before that — a maiden special weight at Churchill Downs on Sept. 11 and the Man O’War allowance on Oct. 17 at Keeneland.

Other trainers, such as 8-1 Uncle Walter’s Michael Maker, have said to watch out for Gun Runner. The word is that Gun Runner, who carried much of the pace in the Jockey Club along with Mor Spirit, was affected by the track conditions but has great talent.

Casse said Gun Runner definitely is a concern.

“He has a great trainer, and he is a great horse,” Casse said.

Tom’s Ready also may be flying under the radar, having finished second to Mo Tom in the Lecomte and the Street Sense and second to Pinnacle Peak in a Fair Grounds allowance. He won a maiden special weight at Churchill on Sept. 28.

He’s also the most experienced, with seven starts. His only bad finish was in the Jockey Club over the bad track.