Spurs risk alienating Vertonghen by continuing to play him there.
Don't blame Andre Villas-Boas. The Tottenham manager has been forced to deploy Vertonghen out of position in wins over Sheriff Tiraspol and Hull City.
With Danny Rose and Zeki Fryers not considered for selection against Hull due to injury, Villas-Boas made the rational decision to start Vertonghen over Kyle Naughton at left-back. Naughton, a right-footer, prefers to cut in and play a pass centrally at left-back that slows down play. Vertonghen, being a left-footer who once scored a brace for Ajax against Vitesse from left-back naturally, was the better option.
Sure enough, it was Vertonghen's cross that caught the hand of Hull's Ahmed Elmohamady that led to a fortuitous penalty for Spurs that Roberto Soldado converted to seal a 1-0 win.
What do you think Tottenham management did to coax Vertonghen into signing on the dotted line?
They must have sold him a bill of goods. He thought he would become an indispensable figure at centre-back alongside stalwart Michael Dawson. Seven days after Vertonghen was announced as a Tottenham player in July 2012, Ledley King retired.
An aging William Gallas (now playing in the A-League with Perth Glory), an injury-prone Younes Kaboul and promising youngster Steven Caulker (later sold to Cardiff City) returning on loan from Swansea City, weren't expected to seriously challenge Vertonghen. You can only assume Spurs management tip-toed around discussions of him being a makeshift left-back.
Last December, Vertonghen, who ended up making 15 league starts at left-back, was asked by reporters if he was frustrated with being played at left-back instead of centre-back.
"Yes, and the manager knows," said Vertonghen, via Sky Sports. "I prefer centre-back but I want to help the team."
Do you remember why he chose Tottenham over Arsenal?
Arsene Wenger wanted to change Vertonghen, who before becoming a full-time centre-back at Ajax had spent extended periods of time in midfield and left-back, into a holding midfielder in the "2" of a 4-2-3-1.
"They [Arsenal] wanted me to be a controller in the midfield, an Emmanuel Petit-type," said Vertonghen, from NUsport via ESPN.co.uk. "Ultimately, I just came to play at centre-back."
When questioned on why he didn't see himself as a full-back, Vertonghen said: "I'm not agile enough to play against players like Nani and [Raheem] Sterling."
Vertonghen's recent performance at left-back for Belgium against Croatia reinforced what he believes is a matchup disadvantage for him when he's tasked to defend against pacey wingers.
Croatian right wing-back Sime Vrsaljko managed to send in 12 crosses, though only one was accurate, when he went head-to-head against Vertonghen.
That said, Vertonghen is selling himself short when he says he isn't agile enough.
If he wasn't agile enough, how did he average 3.1 tackles and 2.9 interceptions per league game last season?
Vertonghen has the capability to track wingers, but the idea of running up and down the left flank isn't appealing to him.
The sad reality of Spurs' current left-back situation is that Vertonghen is the best left-back. Rose is decent but he's yet to show world-class potential. Fryers lacks experience and Naughton is better at right-back.
Vertonghen moving to left-back permanently is an option especially if Vlad Chiriches can replicate his dominant performances against weak opposition in Anzhi Makhachkala and Sheriff against bigger teams.
Vertonghen's situation mirrors that of Gallas when he played under Jose Mourinho at Chelsea.
"Of course I know that the manager has no other option right now other than to play me at left-back," said Gallas, from L'Equipe via Jon Brodkin at The Guardian. "I will accept it for the time being but I have to stress that it is becoming very difficult for me."
Gallas' frustrations later snowballed into deep resentment, culminating in an acrimonious departure from the Blues with Mourinho accusing Gallas of threatening to score an own goal, a claim he denied.
What started as a one-off sacrifice for the good of the team became Gallas' position.
Vertonghen won't want this to be his fate. He didn't join Spurs to be a left-back.