KEY POINTS:
If David Walsh is right Rios should add tomorrow's $320,000 First Sovereign Trust 2000 Guineas to his growing list of achievements.
Walsh has always maintained the further Rios races over the better he'll get.
Rios went 1400m when he won the Guineas at Ellerslie, stepped to 1500m to take the Wellington Guineas and for the first time goes to 1600m for his biggest assignment yet.
It wasn't just the distance Walsh was referring to when he made his Rios predictions - part of the equation was the handsome colt's development with time.
Despite the runs by Rios at Ellerslie and Trentham, tomorrow's group one classic will be extremely difficult.
Alamosa, the horse he beat by just a nose at Trentham, is improving, The Pooka appears to have found his best form at the right time and even Pierre Joseph, something of an enigma at times, showed with his fourth in the Wellington Guineas that he's close to winning a big one.
Apart from a wealth of talent, in Rios' favour is that he is the perfect racehorse.
He relaxes on any speed, will pick it up immediately when his rider says go and he does not lack fight in a tight finish as he displayed at Trentham.
Alamosa, from the No 1 barrier, and The Pooka from No 3, are almost certain to be in front of Rios when they head into the home straight.
Alamosa had to switch ground in the last 300m at Trentham and with only a nose between him and Rios that might have cost him dearly.
The Pooka, who has always looked good, went through a difficult second half of last year's juvenile season, but came back with a couple of superb efforts in the Hastings spring triple crown.
His win on the first day, albeit against easier opposition than this, was top class.
Trainer Peter McKay said Alamosa has travelled to Christchurch in good order and he was pleased with the horse's work at Riccarton yesterday.
