It is the first time the 29-year-old has been picked for Germany's senior squad. Petersen's values might not be obvious at first sight but Loew's gut feeling, as he said himself, led him to choose the Freiburg striker over other candidates like Bayern Munich striker Sandro Wagner, reports Xinhua news agency.
Uncapped Petersen is regarded to be a certainty for the final squad of 23 that Loew has to announce on June 4 following the two-week training camp.
But why select the man who is hardly known by the German football public? According to the Bundesliga's scorer list, the striker is the best German-born striker of the 2017/2018 season, having scored 15 goals.
Petersen is considered to be the perfect super-sub. No other player has scored more goals (20) coming off the bench.
Petersen played nine games for Bayern Munich (two goals) in the 2011/2012 season but disappeared from the radar after failing to perform consistently for the Bavarians. Via Werder Bremen, the center forward joined Freiburg in the 2014/2015 winter-break and was relegated to the second division.
After staying with Freiburg, 21 goals made him the lower league's top scorer and it helped his club make an immediate return to the Bundesliga.
Petersen never complained when losing his place in the starting eleven but continued to support the team.
Last winter Petersen was appointed as team captain in Freiburg. "Nils scored 15 goals for a team that is not famous for creating that many chances. That speaks for itself," Loew said.
In one way, his nomination does not come as a total surprise, as Loew has a habit of producing a player that no one previously had on their radar.
Loew, to everyone's surprise, was in the stands for Freiburg's last game of the season against FC Augsburg. Whilst the coach still owns a house in Freiburg, the league's final fixtures had other games full of World Cup candidates. Critics said he could have gained important information by visiting another match.
Petersen is becoming the man for surprising nominations. In 2016, he was amazingly selected for the Olympic football team that claimed the silver medal.
Petersen scored six goals to make him the tournament's top scorer. He also increased his reputation as the ideal team player, so much so that he earned high praise from the coach and former German international, Horst Hrubesch.
Now Petersen is part of Germany's preliminary squad alongside better-known performers like Thomas Mueller (Bayern Munich), Mario Gomez (VfB Stuttgart), Marco Reus (Borussia Dortmund), Timo Werner (RB Leipzig) and Leroy Sane (Manchester City).
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