Chelsea were ready to pay £52 million, about €61 million, and to send Jamie Bynoe-Gittens to Rome on loan on the last day of the summer window, La Gazzetta dello Sport reported at the time.
The deal collapsed largely because Gian Piero Gasperini refused to lose a cornerstone of his midfield with only hours left to find a replacement.
Gazzetta pointed out that Koné's balance-sheet value was only just over €10 million, so the sale would have brought AS Roma a profit of around €50 million. Gasperini's argument was that the team was already working well and that a departure in July or early August would have been a different matter.
Three weeks later, the decision looks well judged. Koné scored twice in the first half of Roma's 2-2 draw with Inter on Saturday, in the 6th and 37th minutes, before Lautaro Martínez answered with two goals of his own after the break. The draw left Roma and Inter level on 13 points at the top of Serie A, and Koné was replaced by Niccolò Pisilli on the hour.
Corriere dello Sport now puts his valuation at around €100 million. It described his display against Nicolò Barella and Piotr Zieliński as total, combining running, physical strength, personality, ball recoveries and late runs into the area, and credits Gasperini for reshaping him from a midfield destroyer into a player who attacks the box and decides matches, with Bryan Cristante staying deeper so that Koné can operate closer to the opposition area.
His profile has also grown on the international stage. Koné started four of France's first six games at the World Cup, but was left out of the semi-final line-up. A minor injury slowed the start of his season, and that he still struggles to last the full 90 minutes, but that he has been decisive whenever he has been on the pitch.
Roma have no intention of selling him for financial reasons, a message that was delivered to Chelsea. Their next league game is away to Como on 11 October.