When Gylfi Sigurdsson volleyed home Jefferson Montero's cross, critics were quick to blame Spurs left back Ben Davies for lax marking. In truth, a combination of quality play by Swansea and poor communication among Spurs' midfielders and defenders caused the breakdown that left Sigurdsson wide open.
The play starts when Swansea take a throw-in from inside their own half. Nabil Bentaleb and Roberto Soldado press Swansea's defensive midfielder Jack Cork, who passes backward to Ashley Williams. Soldado chases after the ball but pulls out of a 50/50 challenge with the bigger Williams, who switches play to Swansea's left back, Neil Taylor.
Taylor (out of picture) is all alone on the left as Spurs have pushed all of their attackers and midfielders to the side of the pitch where the throw-in took place. Taylor takes one touch, then plays the ball down the flank towards Jefferson Montero, who is isolated against Kyle Walker on Swansea's left wing.
Though Walker is struggling to deal with Montero's pace, Spurs are not in trouble yet. As can be seen in the image above, Eric Dier and Jan Vertonghen are marking Nelson Oliveira, Davies is marking Wayne Routledge, and Bentaleb has picked up Sigurdsson.
As play progresses, however, Swansea's attacking players' movement, simple though it is, confuses Spurs defenders and midfielders. Oliveira positions himself for a cutback while Routledge darts toward the middle of the six-yard box. Davies follows Routledge, perhaps in the belief that Bentaleb has stayed with Sigurdsson.
Bentaleb, however, ends up in no man's land, neither marking Oliveira nor Sigurdsson. Sigurdsson notices the confusion and peels off to the back post, where he is unmarked. Walker fails to force Montero towards the help defending of Ryan Mason, and his cross finds Sigurdsson for the goal.
As is often the case, this goal was the result of multiple breakdowns, not the lax defending of a single player. Roberto Soldado's failure to challenge Ashley Williams, Kyle Walker's inability to slow down Montero, and the collective failure of Bentaleb and Spurs' defenders to communicate all played a part in the goal. If Spurs are to make a push for the Champions League places, Mauricio Pochettino must fix these issues quickly.