Doncaster Group 1 gives Aidan O'Brien another chance to play with his fascinating juvenile jigsaw puzzle

I'm slightly dreading a brilliant performance from Diego Velazquez in the Kameko Futurity Stakes at Doncaster on Saturday, odd-sounding words that reflect an internal conflict in my racing brain.

The idea of an unbeaten juvenile doing his stuff in a defining end-of-season Group 1 race – assuming of course that Doncaster survives the weather – is exhilarating and enthralling. I would love to see the Aidan O'Brien-trained colt, a Group 2 winner over a mile at Leopardstown on Irish Champion Stakes day, emerge with flying colours from his probable clash with rivals such as Ancient Wisdom and Dancing Gemini.

However, an extravagant display would prompt mixed feelings. I reckon I have already seen two exceptional O'Brien-trained juvenile colts this season in City Of Troy and Henry Longfellow, either of whom look capable of completing a Guineas/Derby double. Can we cope with a third? Is it realistic?