The ESPN pundit claims that the Spaniard mismanaged his former Everton player.
The Spanish manager was sacked by the Toffees in May after leading Everton to an 11th-placed Premier League finish for the second season in succession which, given the talent he had at his disposal, may well be significant underachievement on his part
One of the talents he had was of course centre-back Stones, who was the subject of repeated bids by Chelsea last summer but then-owner Bill Kenwright stuck to his guns and rejected a number of big-money offers for the 22-year-old - the largest of which was £38 million, according to The Independent.
Despite that, Stones did not have a fantastic season under Martinez and ultimately divided opinion among supporters as to whether Everton should have cashed in when they had the chance.
Nevertheless, the ball-playing defender remains in demand it seems and Stones himself told his club's hierarchy that he wanted to join Pep Guardiola's Manchester City - according to ESPN - who are willing to pay £50 million for his signature.
Nicol has now suggested that the youngster needs a manager who will take care of him, intimating that Martinez did not do a great job at that, whilst suggesting that he has "huge potential".
"He has to go somewhere where the coach is going to look after him," he told ESPN. "I don't think Martinez looked after him properly.
"I think he's got huge potential. For me, he's potentially the best young centre-halves in the Premier League."