John F Kennedy lost his place as favourite for the Investec Derby after finishing a well-beaten last of three on his seasonal debut at Leopardstown.
There was a major shake up in the betting for Epsom Classic, with the Aidan O'Brien-trained colt being replaced as market leader by his stablemate Ol' Man River.
The latter was promoted to head of the market at 6-1 with BetVictor as John F Kennedy was eased out to 7-1 from 7-2 after finishing last of three behind race-fit Success Days (10-1) in the P.W. McGrath Memorial Ballysax Stakes.
Shane Foley ensured a true test by setting a solid pace on the Ken Condon-trained colt.
The writing was on the wall early in the straight as Success Days kicked clear to win unopposed by four and a half lengths from Zafilani, with 1-4 shot John F Kennedy and Ryan Moore a further six lengths away.
"We said we'd make use of him as he had the run under his belt and possibly had the edge in fitness," said Condon.
"The other two were always going to want a lead and it worked out great. I'm delighted.
"He's in the Irish Guineas, but has no other fancy entries. I think the Irish Derby is later closing now and that's something we could look at.
"I'm sure the favourite will come out and do great things in the summer, but it was our day today.
"He got a little bit anxious in a Listed race here last year and we drew a line through that. He was good at Cork and here today."
A great day for Foley got even better when the Jessica Harrington-trained Princess Aloof (16-1) claimed the concluding Follow Leopardstown On Facebook Handicap.
Harrington said: "I nearly didn't run her as I thought the ground would be too soft, but she was ready to go and I'm delighted with her.
"She'll keep going during the summer. She's won at two, three and four now."
Trainer Dermot Weld and jockey Pat Smullen followed up their four-timer at Gowran on Saturday with another four courtesy of Zannda, Zawraq, Stormfly and Zafayan.
Zawraq was a big mover in the Classic markets after running out an impressive winner of the Leopardstown 2,000 Guineas Trial.
Conqueror of the well-touted Sir Isaac Newton on his only start as a juvenile, the 11-8 favourite looked the part as he swept clear in the final quarter-mile to beat Endless Drama by three and a half lengths.
RaceBets quote the Shamardal colt at 12-1 from 25-1 for Epsom and 14-1 from 20-1 for the 2000 Guineas.
Weld said: "It was an excellent performance by a horse coming back.
"My immediate comment would be that I'll discuss things with Sheikh Hamdan as he has a lot of horses in England entered in the Guineas.
"I've always considered him a horse capable of making into a Derby horse and the decision will be whether we go for the English Guineas or wait for the Derrinstown Derby Trial.
"He will stay more than a mile and I actually see him as a Derby horse.
"Hopefully he's a stayer with speed and I think he has a lot of ability."
Stormfly (4-1 joint-favourite) hardly gave her supporters an anxious moment as she swept to an emphatic victory in the Leopardstown 1,000 Guineas Trial.
Blinkered for the first time, she pulled clear in the final furlong to score by three and three-quarter lengths from Devonshire.
"She had to battle hard to win on her previous start and was a very fit filly coming here. She just did enough last time but obviously progressed," said Weld.
"We'll maybe look at the French Guineas. She's tough and genuine, she idles a bit and is a lazy filly. She only does what she has to. She's the sort of filly that could suit that sort of race.
"She has a wonderful temperament and is really laid back. The blinkers just make her concentrate."
Zannda (4-6 favourite) dug deep to take the 10-furlong Irish Stallion Farms E.B.F. Fillies Maiden by half a length from Wedding Vow.
Weld said of his Irish Oaks-entered winner: "She's a nice filly and did her job, she did what we expected her to do.
"She'll appreciate better ground and will hopefully make a lovely filly over a mile and a half as the year progresses."
Zafayan (11-4 favourite) completed the Weld-Smullen quartet when landing the Leopardstown Club 25 Membership Handicap.