Provided they get past their play-off tie, Liverpool will be playing Champions League football once again next season.

Their top four finish is a tangible sign of the progress they've made under Jurgen Klopp, but the German manager also enjoyed lots of success in his previous post.

Before moving to Anfield, Klopp was in charge of Borussia Dortmund, winning two Bundesliga titles, one German Cup and reaching the Champions League final during his seven-year stint.

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One of his greatest success stories has to be Robert Lewandowski, who he brought to Dortmund back in 2010 for just £4 million from Lech Poznan.

The Pole has developed into arguably Europe's most complete striker, and now the incredible lengths Klopp went to before signing the current Bayern Munich superstar have been revealed.

How far Klopp went to sign Lewandowski

Borussia Dortmund scout Artur Platek recently opened up about the things Klopp did prior to submitting a bid for Lewandowski - and it's safe to say the Liverpool boss did his homework.

Platek told Polish news outlet Przeglad Sportowy, via Liverpool Echo: "From what I know, Robert Lewandowski was observed more than 30 times.

"That included secret visits by Jurgen Klopp at the stadium in Poznan, in (a) cap and with a hood pulled over his head."

He continued: "Borussia (Dortmund) could not take a large financial risk at the time, which is why coach Klopp personally went to scout Robert."

So, Klopp left no stone unturned before signing Lewandowski, acquiring all the information he needed and even tagging along on scouting missions to Poland in a disguise.

Lewandowski under Klopp

It does sound like something the charismatic 50-year-old would do, and it certainly turned out to be a decision which didn't backfire because the Polish superstar was exceptional.

Lewandowski scored 103 goals in 187 games during his four seasons under Klopp before joining Bayern upon the expiry of his contract in 2014.

If it was even possible, he's become even better since moving to the Allianz Arena, scoring a whopping 110 goals in just 147 matches for the German champions thus far.

His rise is highlighted by the fact that he's registered more goals in three years at Bayern than he managed in four at Dortmund - and he's not 29 until August.

"Lewangoalski" represented unbelievable value for Dortmund, he was money well spent and Liverpool fans will hope that Klopp's transfer dealings this summer are just as successful.

What do YOU make of this brillant story with Klopp and Lewandowski? Leave YOUR thoughts in the comments box below!