United tried to sign Lewandowski

Van Gaal's reign at Manchester United is one he holds sour memories of. After failing to impress the Old Trafford faithful, the Dutchman was relieved of his duties in May 2016. 

Speaking to 'Bild,' the ex-United boss revealed that he tried to bring Polish striker Lewandowski to the Premier League: "The price was not a problem for Manchester United, but Bayern did not want to let him go."

Munich were unwilling to hand him over, and it's clear why. Lewandowski has been their most prized possesion lately and his record speaks volumes of his ability. 

With 142 goals in 183 appearances for the German champions, Lewandowski has quickly established himself as one of the best strikers in the world. Van Gaal will feel it's a shame that he didn't get the chance to train him at United.