LEXINGTON, Ky. – Michael Matz was a medal-winning Olympic equestrian, saved four children from a burning airplane, and trained a legendary horse named Barbaro to win the Kentucky Derby. But the poor guy still has no control over the weather. That’s why Matz, as stalwart a figure as he is, has been a little wishy-washy about when he will be giving Union Rags his next workout. Given the proverbial “wait 15 minutes for the weather to change” conditions that prevail in the Kentucky springtime, Matz, as of Wednesday, had not yet decided on time or place, although the one sure thing is that it will come Saturday or Sunday. “It’s supposed to rain this weekend, and if it’s too wet, we’ll just stay here” at Keeneland to work, he said. “But if it turns out nice, I would like to van him down” to Churchill Downs. Like quite a few of the prospects for the 138th Kentucky Derby, Union Rags will have two more workouts prior to the May 5 race – one this weekend, and a final work a week or so from the race. Some of the others, including the ones that raced last weekend – notably Dullahan and Hansen from the Blue Grass Stakes, and Bodemeister and Secret Circle from the Arkansas Derby – are down to just one final breeze. [DERBY WATCH: Top 20 contenders | Who's hot, who's not] Matz, 61, said the final work for Union Rags definitely will come at Churchill. The trainer said he is happy with how the colt has acted and trained since arriving in Lexington on Sunday from Florida, where he spent the winter as the clear-cut favorite for the Derby until finishing third as the 2-5 choice in the March 31 Florida Derby. With just a little more than two weeks to go, the Derby field is pretty much set, and yet favoritism seems very much up for grabs among this handful of horses: Union Rags, Bodemeister, Dullahan, Gemologist, and Creative Cause. A few changes to what might be termed the lower tier of the field typically come during the final days before entries are taken the Wednesday morning before the race (May 2), but as of now, nothing is altering the upper crust. The Grade 3, $200,000 Coolmore Lexington Stakes, for which entries were drawn Wednesday, could produce a Derby starter when it is run Saturday at Keeneland, but only if Castaway or Morgan’s Guerrilla emerges the winner from a field of 11. Castaway, with $162,000 in graded earnings, would crash the 20-horse list by taking home the $120,000 winner’s share, while Morgan’s Guerrilla ($100,000 in graded earnings) still might need some luck to make it, depending on what develops until entry time. One other Lexington starter, Holiday Promise, has $94,000 in earnings from his runner-up finish in the Grade 3 Vinery Spiral last month at Turfway Park, but he is not a Triple Crown nominee and would have little to no chance even in case of a victory because of rules that relegate supplementary entries to the rear of the line. [MIKE WATCHMAKER: New favorite in Derby Watch] Two other graded races remain on the Triple Crown trail, although the $200,000 Jerome, to be run Saturday at Aqueduct, will have no impact on the Derby, while the same is likely to be said about the $200,000 Derby Trial on opening night, April 28, at Churchill. As for the horses for whom varying degrees of doubt have lingered in recent days: ◗ Liaison ($393,000) worked six furlongs in 1:13 Wednesday at Hollywood Park and “remains a candidate” for the Derby, said trainer Bob Baffert, adding he is taking things “day by day” with the colt and feels no urgency to make a decision. ◗ Alpha ($380,000) had a routine gallop Wednesday morning at Belmont Park and appears to be recovering well from an infection he developed after getting a few cuts on his left shin during his runner-up effort in the April 7 Wood Memorial. He is tentatively scheduled to be flown April 30 to Louisville. ◗ After several days of saying he and owner John Oxley would wait until about a week before the race to make a firm decision, trainer Mark Casse on Wednesday said Prospective ($367,327), sixth in the Blue Grass, definitely will go in the Derby. ◗ Trinniberg ($324,500) remains “85 percent doubtful” to run in the Derby, according to trainer Bisnath Parboo, and would wait instead for the Preakness. ◗ Trainer Jerry Hollendorfer said a decision will be made this week whether Rousing Sermon ($270,000) will run in either the Derby or remain in California to run in the April 28 Snow Chief Stakes versus statebreds. ◗ El Padrino ($250,000) is being trained as if he will make the Derby and is scheduled to work Sunday at Palm Meadows in Florida, according to Todd Pletcher, who also will work Gemologist there the same morning. ◗ Reveron ($220,000), while initially considered for the Lexington by trainer Agustin Bezara, instead bypassed the race in the realistic hope of making the 20-horse cut and will ship Sunday to Churchill from south Florida. In other news, Mark Valeski, now almost certain to make the race, was among a load of horses that trainer Larry Jones sent Tuesday afternoon from Keeneland to Churchill. The 2011 Horse of the Year, Havre de Grace, was also among those vanned over. Also, trainer Hamilton Smith said from Maryland that Illinois Derby winner Done Talking will work at Laurel Park the next two Saturdays before being vanned to Churchill on April 29. – additional reporting by David Grening and Steve Andersen