The 20-year old Nigeria-born star and three others that may replace Haaland at Dortmund

Erling Haaland's departure from Borussia Dortmund appears to be getting closer, with Manchester City, Real Madrid and Barcelona the frontrunners to pay the €75 million exit clause in his contract. 

With a remarkable scoring ratio of a goal per game (80 goals from his 80 appearances for the club in all competitions), the Norwegian's boots are going to be big ones to fill.

They must be filled nonetheless, though, so who could possibly replace 21-year-old Haaland as the primary goal threat at Westfalenstadion? 

With a long-standing tradition of launching high-scoring, out-and-out goal scorers -- Robert Lewandowski and Pierre-Emerick Aubameyang are two prime examples from the past decade, though Ciro Immobile didn't quite work out -- Dortmund's attacking brand of football often proves kind to a sharp No. 9.

It's only a matter of time before the release clause in Erling Haaland's contract clause is triggered and he departs for one of the European giants, leaving Borussia Dortmund with massive boots to fill.

Here are a few names that Dortmund might consider.

Karim Adeyemi, 20, FC Salzburg | Transfer value: €35m

 Although Adeyemi -- incidentally, Haaland's replacement at Salzburg -- is already a well-established target, Dortmund's interest seems to have dwindled with the 20-year-old's recent drop in form. Having enjoyed a formidable start to the season, including a debut senior goal for Germany, Adeyemi has struggled to make a similar impact since the turn of the year. (His only goal came from a last-minute penalty in the league against Altach).

 According to media reports, Dortmund are reluctant to pay the €42.5m transfer fee demanded by the Austrian champions.

The occasional goal drought is not uncommon for young forwards, and Adeyemi has previously proved that he possesses the quick finishing technique, pace and strength of a budding top-level striker, plus intelligent off-the-ball running.

If it's not Dortmund for Adeyemi this summer, he's certain to be picked up by a big club sooner rather than later.

As it happens, Karim Adeyemi was Erling Haaland's replacement at FC Salzburg, and the German could be following in his footsteps once again. Getty Images

Darwin Nunez, 22, Benfica | Transfer value: €40 million

The performances of Nunez might suggest that he's about to move into a category of players who are off limits for all but a dozen European elite clubs, which means that Dortmund's chances of landing the powerful Uruguayan are quickly fading. When it comes to playing style, Nunez has the mobility and powerful right foot that fits the profile of many elite strikers, but does share a few similarities with Haaland in particular: he's at his best when the game opens up and there's the chance to make quick, sharp early movements across the opposing defensive line.

Luka Jovic, 24, Real Madrid | Transfer value: €20 million

Very little has worked out for Jovic since he left Eintracht Frankfurt in 2019 following an exceptional campaign. At just 20, the Serbian striker scored 19 Bundesliga goals and contributed significantly to his side's journey all the way to the Europa League final. Having been rewarded with a €62m move to Real Madrid, the once-prolific goal scorer has seen only sporadic glimpses of his former self. A loan move back to Eintracht Frankfurt last season proved unsuccessful and since returning to Spain, Jovic has managed only the odd substitute appearance under Carlo Ancelotti.

Sasa Kalajdzic, 24, Stuttgart | Transfer value: €22 million

The towering, 2-metre-tall centre-forward returned to action only after the Bundesliga winter break following a shoulder injury that kept him out for nearly half a year. A signing from Admira Wacker in the summer of 2019, Kalajdzic is a late bloomer who first properly announced himself at the highest level with 16 Bundesliga goals last season.