Katarina Johnson-Thompson can be an even better heptathlete than Jessica Ennis-Hill, says Toni Minichiello.
Briton Johnson-Thompson is sixth at the World Athletics Championships - which Ennis-Hill has been forced to miss through injury - after four events.
Ennis-Hill's coach told the BBC: "She is better than Jessica pound-for-pound.
"If you look at what Jess did at her age as a junior, Kat's performed better than that every single time. If she keeps going she'll probably be better."
The Liverpool athlete, 20, clocked 13.49 seconds in the opening event - the 100m hurdles, just 0.01 outside her personal best, and followed it up with a clearance of 1.83m in the high jump, narrowly down on her season's best.
She managed just 11.52m in the shot put - one of her weakest disciplines - but ended the day on a high with a personal best of 23.37 seconds in the 200m.
That put her on 3739 points, 97 off American Sharon Day in bronze medal position, with Ukraine's Ganna Melnichenko leading on 3912 with three events remaining.
Johnson-Thompson said: "I had a good start in the hurdles with 13.49, and I was quite happy with where I finished in the 200m, it was just the high jump and shot put that let me down."
Although Minichiello believes in Johnson-Thompson's potential, he thinks a medal in Moscow remains a tall order for her this early in her career.
He added: "I think that a medal will be a stretch for her, I think a top-eight finish is what you are looking at."
Johnson-Thompson's accomplishments in her fledgling career include heptathlon gold medals at the World Youth Championships in 2009 and European Under-23 Championships this year and in the long jump at the World Junior Championships in 2012.
Meanwhile, Ennis-Hill, 27, finished fifth and eighth respectively in the heptathlon at the 2003 and 2004 World Youth Championships, having led both at the end of the opening day.
She also claimed two silver medals in the 100m hurdles and high jump at the 2004 Commonwealth Youth Games and gold at the 2005 European Athletics Junior Championships with a British junior record score of 5,891 points, however Johnson-Thompson has since surpassed her as British junior record holder.
Olympic champion Ennis-Hill wished her compatriot all the best for the World Championships, writing on Twitter: "So strange not to be out there at the worlds! Wishing @JohnsonThompson lots of luck though. Good start :)."