Two-and-a-half years on, some Spurs supporters are suddenly indignant he was allowed to leave the club, fuelled in part by a candid claim by their manager.

"I think after he moved to Swansea and we saw his development, he was a perfect player for us. It's a shame," Mauricio Pochettino said of Sigurdsson before Spurs hammered Swansea 5-0 in December. The 27-year-old was subdued as a False No.9 that day but it's easy to see where Pochettino is coming from.

The Iceland international has scored eight goals and has eight assists in the league this season. The five players to have directly contributed to more goals are all strikers playing for top seven clubs, putting Sigurdsson above Eden Hazard, Dele Alli, Kevin De Bruyne, Mesut Ozil, Juan Mata and every other playmaker in the division. Of Swansea's 31 league goals, he has scored or assisted more than half. There have been three penalties but at least three fine goals, too.

His form led to a "substantial offer" from another club -- Everton or West Ham were linked -- in January and Spurs fans aren't the only ones wondering how Sigurdsson became the one that got away.

"It's a bit of a mystery to me why it didn't happen for Gylfi Sigurdsson at Tottenham," said Graham Souness this week. "He could comfortably play for a club in the top half of the Premier League."

Sigurdsson would do well at Everton or West Ham, but it's no mystery why he was sold by Spurs in summer 2014. He is fondly remembered at the club but he was never particularly effective at White Hart Lane. A loan spell at the Liberty Stadium, where he scored seven times in 18 appearances in the second half of the 2011-12 season, convinced Spurs to buy him but he managed just one more goal than that in 58 league appearances for the London club. He has scored as many this season already.

That's because in two years at Tottenham, Sigurdsson made more appearances from the bench than starts and when he did play it was rarely in his best position at No.10. First Gareth Bale and then Christian Eriksen were preferred there and he was shunted to the left flank by head coach Andre Villas-Boas.

"I would have liked playing more games in the middle. This is why I had to go to Swansea. I didn't want to stay on the bench for another year," Sigurdsson said last year.

Without a team tailored to him and in an unfamiliar, tactically demanding role, Sigurdsson showed his limitations as a footballer under Villas-Boas. He couldn't track back, he couldn't link-up with the full-back, he couldn't provide any width and while Spurs' best attacks in those joyless days between Bale's sale and before Villas-Boas' departure often involved him, he didn't influence games as he is now in South Wales.

There is nothing to suggest it would be any different under Pochettino. Tottenham still have Eriksen -- who, by contrast, has adapted superbly when asked to play wide -- and now they have Alli too. If Sigurdsson had stayed at White Hart Lane, or if he was to become the first player in Premier League history to go from club A to club B to club A and back to club B again, he would be back on Tottenham's bench.

Sigurdsson has lots of qualities -- there are few better players over a dead-ball or popping up in space around the box -- but he is ill-suited Pochettino's high-octane football or an environment where responsibilities on the pitch are increased but overall responsibility for the team is decreased. It is hard not to think that Pochettino was being charitable to a well-liked character when he publicly lamented selling Sigurdsson. And why not?

"Every time we meet him and see him he shows his quality not only as a player but as a man. All the people here talk very highly about him," Pochettino said in December.

A rewriting of Sigurdsson's time at Tottenham is understandable, particularly while he is free-scoring and his former club have reverted back to wondering where the next goal is coming from.

The Iceland international's impressive tally this season includes goals against Chelsea, Arsenal, Liverpool and Manchester City -- more evidence that he thrives on the responsibility of being Swansea's most important player. He can be most effective for Tottenham in scoring against their top four rivals, rather than sitting on their bench again.