The 27-year-old left Tottenham Hotspur back in 2014.
Mauricio Pochettino described Gylfi Sigurdsson as a "perfect player" for Tottenham Hotspur before he returned to White Hart Lane with Swansea City last week.
The Iceland international was sold by Tottenham's board - not Pochettino - two years ago in what was effectively a swap deal, with Ben Davies coming the other way.
Time has proven that it was not a great deal by Daniel Levy, with the 27-year-old netting 23 Premier League goals for the Swans and setting up another 18 since leaving, whereas Davies has been a fringe player for the most part since joining.
If his pre-match comments last week were anything to go by then Pochettino is obviously a huge fan of Sigurdsson and the Argentine should convince Levy to right his wrongs and try bring him back to North London in January.
Defensively, the Lilywhites have been outstanding for the most part this season but they have struggled at the other end. The four teams ahead of them in the table have all scored significantly more than Spurs, who have 24 goals in 14 matches.
Of course, Harry Kane's six-week absence would have contributed to that figure. It would've been more had the 23-year-old been available, but it could be a lot more with a provider of Sigurdsson's class behind Kane.
Dele Alli is going to be a big star in football but he has struggled to kick on from his exceptional standard last season, setting up one goal in 13 league matches so far.
It isn't enough for a number 10 in a team with title aspirations, but adding competition would relieve him of a bit of pressure and allow him to develop a little more. It's worth remembering that he is only 20 - and only human, despite what last season suggested.
It is also worth remembering that Tottenham are now a Europa League team and they will have to contend with the rigourous Thursday-Sunday schedule. Rotation will be important to juggle both competitions without effectively throwing one or the other, like Pochettino did with the Europa League last term.
Swansea won't let him go easily. At the moment, he is looking like the only weapon they have in their fight against relegation.
He would be a lot cheaper in the summer if City do drop down into the Championship, but the competition for his signature would also be fierce and would he rejoin Spurs if, say, another big club wanted him? After being deemed not good enough for Tottenham once already by the club's hierarchy, probably not.
But the North Londoners can fess up to their error by making a move in January and it would look better if they do it sooner rather than later.