If you had to point to Jose Mourinho's biggest mistake since his return to Chelsea, it would probably his decision to jettison Kevin De Bruyne.
The Belgian became a huge hit at Wolfsburg and returned to the Premier League with Manchester City this summer, where he has been in fine form.
Could a similar situation unfold involving Thorgan Hazard? Having been loaned to Borussia Monchengladbach last season, Hazard made a £5.9m permanent move to the German club last summer and has cut an impressive figure during his side's Champions League campaign.
His form has prompted Spurs to have the attacking midfielder watched by their scouts, who were present to watch Gladbach's game against Juventus in midweek.
Chelsea are said to have a buy-back deal in place, but with relations seemingly frosty between Jose Mourinho and Hazard's brother Eden, could Tottenham steal away another talented young player from the Blues?