It would be better for Chelsea and Marco van Ginkel if he was playing elsewhere this season.
Christian Eriksen has moved to Tottenham (h/t BBC). That leaves a hole in Ajax's midfield, one they hoped to fill with van Ginkel on a season-long loan. According to Metro's Hannah Duncan, the Blues have rebuffed the reigning Eredivisie champion's advances.
Ajax's director of football, Marc Overmars said, "We would like to see van Ginkel playing at Ajax. For that type of player we are willing to pay top price. I’ve tried, but Chelsea will not let him go."
It's a move Chelsea need to really rethink again before the transfer window closes.
The 20-year-old van Ginkel made the move to Stamford Bridge this summer for £8 million. It was a great piece of business for Chelsea because van Ginkel is an immensely talented footballer and can be the long-term replacement for Frank Lampard.
Unfortunately, Lampard is not done just yet. He's still got another year left in the tank. While the 35-year-old can't play 40 matches this season, he's still good enough to be the regular partner for Ramires in Jose Mourinho's 4-2-3-1 formation.
Mourinho has already said that he plans on using van Ginkel this season. It wouldn't be the first time, though, that a manager has said a young player will get playing time, only to instead rely on the older, more established veterans. It's not like he's going to say that one of his most recent purchases has no hope of getting in the first team.
Van Ginkel needs to get first-team football each and every week, and Chelsea don't seem in a position to guarantee him that. Perhaps it would be better that he goes to Ajax, where he'll get regular starts and also play in the Champions League group stage.
Chelsea don't need van Ginkel this season. Aside from Lampard, they've got John Obi Mikel, Mikel Essien and Josh McEachran who could fill in in the midfield. Mourinho could also move David Luiz up from centre-back or drop one of his attacking midfielders into a deeper position to increase his options.
The club has had a lot of success loaning out Thibaut Courtois and Kevin de Bruyne while their paths to the first team are blocked. While Courtois is on loan again at Atletico Madrid, de Bruyne returned this summer after a year at Werder Bremen a much better player and should be a key player for Mourinho.
By sending van Ginkel to Ajax, Chelsea would be ensuring he's continuing to improve. Then, when he returns in a year, Lampard will be a year older and far less equipped to be the regular starter in midfield.