Chelsea boss Thomas Tuchel insists he "expected more" from Billy Gilmour after the midfielder departed the club in a £9m deal to Brighton.
The Scotland international spent last season on loan at Norwich, suffering relegation from the Premier League as he failed to nail down a permanent place in the starting XI.
The 21-year-old return to Stamford Bridge for pre-season, but he was removed from the first-team squad during their trip to the USA.
And Tuchel admits he wasn't convinced that Gilmour was ready to assume a regular role in the Chelsea first team.
"We had high hopes and he played for us in the first half-a-year when I was at Chelsea," said the Blues boss. "He played some important matches for us and looked for a new challenge that did not go so well for him with Norwich.
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"We expected more, he expected more so it was like, without pointing a finger, but it is difficult also for him and for us to not succeed, to not play at Norwich, to be relegated and then suddenly be a central midfielder for Chelsea and competing for top four and for every title. There's a huge step in between so we were looking.
"The ideal solution would have been maybe that he goes again on loan as the concurrence is huge for us in central midfield and we felt like he is not the age where he can live again with five or seven or eight matches during a whole season to fulfil his own potential so ideally it would have been another loan.
"Billy did not want to go on loan, it was a no-go for him so in the end we agreed to a sale."