Salvatore Laporta/Associated Press

At the World Cup in Brazil, during Belgium’s group-stage match against Algeria, Napoli winger and attacking midfielder Dries Mertens was brought on right after half-time. He was asked to salvage a worrying situation.



Despite being branded as potential dark horses ahead of the tournament, Belgium were trailing 1-0, and looked unable to capitalise on the creative capital they had in the form of Eden Hazard, Romelu Lukaku and Nacer Chadli.



The idea was that Mertens, quick and explosive as he was, would run at Algeria’s deep-sitting and undoubtedly tired defence. In a way, he was asked to be the battering ram next to Hazard’s and Kevin de Bruyne’s more methodical approaches.



It took a few attempts, but eventually, the plan Belgium boss Marc Wilmots had envisioned came to fruition.

In the blistering Brazilian heat, Mertens slotted it past the Algerian goalkeeper in the 80th minute. Ten minutes earlier, Marouane Fellaini had already equalised. Belgium won the match.



On the one hand, Mertens' goal seemed like a product of the confidence he had developed during his first season at Napoli.

After making the move to Serie A from Dutch side PSV Eindhoven for a reported fee of £8.1 million, he had scored 11 goals in 33 appearances. He had made a huge step in his career, and it had been relatively successful so far.



On the other hand, the scenario that unfolded during Belgium’s World Cup tie against Algeria seemed to reaffirm Mertens' classification as a super sub. Once again, Mertens had been used when his energy and pace would serve his team best: near the end of the match, when the opposition was tired out from defending non-stop.



While he had made 33 appearances in his first year in Italy, he only played out the full match on 12 occasions. In the remaining 21 matches, he was either subbed on or subbed off and was denied the chance to play for 90 minutes.



"Impact," then, seems like the best keyword to describe the way Mertens has been used by his managers—at club level and during the World Cup.

Rather than as a member of the first XI, the winger and attacking midfielder is often used as a secret weapon, a trick in the bag only utilised in times of need.



Does Mertens have a chance to establish himself as an automatic choice for Napoli this season? Of course he does. He is a skillful, dangerous winger, and his 11 goals in 33 appearances serve as proof of his effectiveness.



The question is, however, whether manager Rafael Benitez will use Mertens that way. With the myriad choices available to him, he might choose to keep the Belgian as the card up his sleeve.