Strongly fancied for the Classic having won the Cheveley Park Stakes at two, she was beaten long before stamina became an issue.
Now back in work, she remains a possible for the Commonwealth Cup at Royal Ascot but Johnston may look to go elsewhere.
“We’re still scratching our heads a bit,” said the Middleham handler. “She seems perfectly well and we’ve seen nothing to suggest she is not in good health.
“Soon we are going to have to bite the bullet and try again somewhere, but quite where that will be hasn’t been decided. Both Guineas were quite strange in a way with a lot of the fancied horses well beaten.
“We’ve just got to put it behind us and move on. She’s working normally, as she was before the race, there appears to be nothing amiss. My horses haven’t been really sparkling and the same may apply to her. We’ve just got to treat her like a normal horse and when she’s screaming at us to run, we’ll go.
“The Commonwealth Cup is still getting serious consideration, but it seems like every three-year-old who has had a hiccup is going there and at this stage it looks the hottest Group One of the year so we might go elsewhere, I don’t know.”
Meanwhile, Viren’s Army will not be supplemented for the Epsom Derby after his owners decided against stumping up the £75,000 supplementary fee.
The three-year-old, who is owned by a Middleham Park Racing syndicate based at Barton-upon-Humber, propelled himself into the Classic frame when landing the Dee Stakes at Chester earlier this month.
He had previously finished third behind So Mi Dar in the Derby Trial at Epsom and connections were considering adding the Richard Hannon-trained colt to the Epsom field.
However, syndicate manager Tim Palin has revealed Viren’s Army will not be heading to Epsom in which support grows for The Gurkha after Aidan O’Brien’s lightly-raced colt turned Sunday’s French 2000 Guineas into a one-horse race.
“A few of the owners were undecided about supplementing, but they’ve had their vote and decided not to. It’s a prohibitive figure and he’s 25-1 to win. If he was around 6-1, the maths would probably stack up,” said Palin.
Don Cossack has been confirmed as the top-rated staying chaser in Britain and Ireland for the second successive year.
Gordon Elliott’s Cheltenham Gold Cup hero has been awarded a mark of 177, which puts him on a par with the likes of Kicking King and triple winner Best Mate and represents a 2lb higher rating than 12 months ago.
Nicky Henderson’s Sprinter Sacre was named the top two-miler following his remarkable renaissance which saw him win a second Queen Mother Champion Chase, three years after his first. His rating of 175 was 6lb higher than that awarded to the best two-mile novice chaser, Douvan.
Thistlecrack’s dominance in the two-and-a-half-mile-plus division for trainer Colin Tizzard and jockey Tom Scudamore earned him a rating of 174, equal to that of Big Buck’s.