Tottenham Hotspur's failure to sign a winger this summer has been exposed this season as a mistake.
The team have been low on creativity especially in big games, scoring only once against Chelsea, Arsenal and Manchester City - which was an own goal.
Costa ended up signing with Juventus instead, joining on an initial £5m loan which Bleacher Report write will cost the Serie A champions £35 million at the end of the season.
At the weekend Costa demonstrated that he really is a 'big game' player, delivering an oustanding performance for Juventus to hand Napoli their first defeat of the season.
Douglas Costa showed an ability to pick the right passes in the final third, and dug in defensively to press from the front.
This season the 27-year-old has scored once and provided four assists, working himself into a prominent role over the past few weeks after a slow start.
It will be too late for Tottenham to move for him now unless Juventus change their minds, but his current form make it likely he will be playing in Turin next season.
The lesson for Spurs is to think big next summer, and bring in top tier talent who can effect big games - at present they don't have enough of these options and it is being exposed.