Jan Vertonghen was Andre Villas-Boas’ fourth-choice left-back when he took up the role as emergency cover against QPR, but now Spurs fans are wondering if the brilliant Belgian should be given the job full-time.

Two short weeks ago the left-back position appeared to be Tottenham’s weakest spot, as Benoit Assou-Ekotto succumbed to a knee problem and his deputy Kyle Naughton was injured against Lazio.

Plan C was Gareth Bale, and it failed miserably as the marginalised Welshman struggled to make any impact in the first half of the following home game against QPR.

Trailing Rangers 1-0 at half-time, Spurs were booed from the field as they retired to their dressing-room, forcing Andre Villas-Boas to adjust his rearguard again.

The result was that Jan Vertonghen was switched from the heart of the defence to the left-back slot which he occupies for his country, with Steven Caulker replacing him in the centre alongside William Gallas.

The change was a roaring success as Spurs came from behind to win 2-1, with Vertonghen leading the charge for Jermain Defoe’s winning goal and earning the man of the match award.

Now the 25-year-old summer signing has scored in his last two games from full-back, heading home to break the deadlock at Carlisle last Wednesday and then surging forward to open the scoring in the historic 3-2 victory at Old Trafford on Saturday.

In doing so he has proved that he is much more than just a hastily-applied plaster for Tottenham’s injury issue – in fact he may well be the best left-back at the club.

Suddenly, Spurs fans are beginning to wonder whether Plan D should become Plan A, and whether Vertonghen should be asked to play this role on a long-term basis.

It would certainly be difficult to move him on this form. It is difficult to find full-backs who are genuinely comfortable at both ends of the pitch – hence the fuss about Kyle Walker since his emergence at White Hart Lane.

And, for all of Assou-Ekotto’s undoubted qualities, he struggles to provide the same ambition, incision and threat on the left.

The Cameroon international has scored four goals in 186 appearances for Tottenham – one of them being a deflected long-distance strike against West Brom this season. Meanwhile, Vertonghen has scored two in the last week from the same position.

Admittedly, one of them was a header from a set piece at Carlisle – hardly an example of devastating full-back play.

However, that simply underlines the value of having an extra big man in the side in addition to the centre-backs – another aerially dominant 6ft 2ins player who can win headers in both boxes.

Vertonghen has all the qualities needed to oust Assou-Ekotto and build a dangerous, lasting relationship with Gareth Bale on Tottenham’s left flank – a prospect which would currently leave Tottenham supporters drooling.

It is also worth noting that his switch into the wide position has not weakened Spurs’ centre. Twenty-year-old Caulker looks fully capable of forming an effective partnership with Gallas, with Michael Dawson offering cover on the bench – and Younes Kaboul will return to boost the rearguard in the new year.

There is certainly merit to the proposition of Vertonghen’s permanent relocation – but it is very questionable whether the Belgian would be happy with it.

While his impressive, seamless versatility is a major asset to his new club, Vertonghen has always made it clear that he has signed for Tottenham to play in the heart of the defence, and to play a central role in Spurs’ future.

“I think really I’m a central defender,” he said, shortly after his move to north London. “I play left-back in the Belgium team because they already have some great central defenders there.

“I can play there, and in the Belgium team I’m happy that I can play in the team because they have a lot of quality players, but my ambition here is to play in central defence – and I think that’s where they want me to play.”

Given Vertonghen’s burgeoning importance to Villas-Boas’ Tottenham and the fact that Spurs beat a number of rivals to sign him, the Belgian’s own feelings on his role are likely to carry some weight.

Spurs have also sold, released or loaned out four centre-backs during the summer, while Ledley King has retired – and they are planning for a future without 35-year-old Gallas, who is in the final year of his contract.

Vertonghen is that future, and he is likely to return to centre-back in the short-term and the longer-term.

However, Villas-Boas may have been surprised by just how good he is at left-back, and it might well have given him some food for thought.

Whatever happens, it is a nice problem to have.

Follow me on Twitter @BenPearceSpurs