He may not be as elegant as Christian Eriksen, as exciting as Dele Alli or as deadly as Harry Kane, but Heung-min Son is still one of the most valuable players Tottenham have.

Though he would not get in Mauricio Pochettino’s first-choice XI if everyone were fit, Son’s contributions simply cannot be overlooked. Last night’s decisive stoppage-time goal at Swansea was his ninth in the Premier League, in which he has made a mere 16 starts.

Overall, he has scored 16 times in all competitions – despite having started only 26 matches. He has driven Spurs towards their Wembley FA Cup semi-final with Chelsea on April 22 thanks to six goals in four ties.

Alli has been rightly praised for his superb work in front of goal, yet he has made 37 starts this term, and has just two more goals than Son.

The South Korea forward’s efficiency is extremely impressive — and not bad for a man who Spurs strongly considered selling last summer, just a year after buying him from Bayer Leverkusen for £22million.

Son delivers at important times, too. The double at Middlesbrough last September secured a 2-1 win. The second goal at Manchester City in January rescued a 2-2 draw Spurs did not deserve.

The following weekend, the 24-year-old scored twice to save his team from embarrassment in the FA Cup against Wycombe, who led 2-0 and 3-2 before Son struck in the last minute to nick it 4-3. Four minutes after coming on at Burnley last Saturday, Son scored again – his third from the bench this term – and Spurs prevailed 2-0.

With time running out at Swansea, Son ran on to the substitute Vincent Janssen’s back heel and forced the ball in off Lukasz Fabianski’s body. Pretty it was not, but the tumultuous celebrations on the pitch, on the touchline and in the stands illustrated its importance.

Even at the time, it looked strange for Tottenham even to consider selling Son. There was strong interest from Wolfsburg and for much of July and August, it looked as though Son would return to the Bundesliga. In the end, Pochettino decided to keep him. How the Argentinian must be glad he did so.

Yes, Son has weaknesses. He misses good chances. He is sometimes slow to see the right pass, his feet and mind are not always on the same wavelength, and he can drift to the margins. But if he had no weaknesses, Son would have cost £50m or £60m, rather than £22m. Rather than examining his defects, consider what he brings to a team. Beyond the 16 goals, there is the versatility. Son’s best position is on the left of a 4-2-3-1, cutting on to his right foot, yet he has rarely played there this season.

Instead, he has operated as a makeshift centre-forward when Kane has been out injured, as one of two players behind Kane when Pochettino switched to 3-4-2-1, or wherever required when he is introduced from the bench.

Because he adjusts quickly to the pace of a game, Son is a highly effective substitute. He is nearly as proficient with his left foot as his right. He makes clever, unselfish runs to create space for team-mates.

His fitness record is also excellent: apart from missing six games in autumn 2015 due to plantar fasciitis, a condition that causes pain in the heel, Son has usually been available and has already played 78 games for Spurs. His efforts have helped them remain unbeaten in the league when Kane has been missing. The win in South Wales means they have won five and drawn three without their top scorer. Though Son does not catch the eye as much as others, he is still a gem. There is interest in him from Germany, Spain and Italy, but Pochettino and his chairman Daniel Levy must think long and hard before accepting any offers.

Though they left it late, the win was testament to Tottenham’s fitness, hunger and persistence. Against a side who scored early through Wayne Routledge and sat deep for much of the remainder of the game, Spurs struggled to create chances, testing Fabianski only during the final 15 minutes of the match.

After Fabianski had saved from Janssen and Alli, the England midfielder equalised when Eriksen’s volley deflected off Alfie Mawson and fell at his feet. Son then made his mark in stoppage time before Eriksen, who had a superb match, finished a counter-attack with a classy strike.

“You would like to have all your players available but this season we are showing we are a team,” said Pochettino. Without Kane, Victor Wanyama, Hugo Lloris or Danny Rose, this was an impressive effort.

And with home games against Watford and Bournemouth to come, Spurs will believe they can maintain the pressure on Chelsea.