#2 Alexis Sanchez
Sanchez was rated highly in 2011 by Pep Guardiola, who sanctioned a move for the young Chilean forward from Udinese to Barcelona. He became the first ever player from Chile to play for Barcelona. Capable of playing anywhere in the attack, Alexis impressed one and all with his work ethic and dedication towards the Barcelona way of playing. He won 6 major trophies for Barca while scoring 47 goals in 141 appearances in the process.
Alexis joined Arsenal in 2014 for more game time but has been left frustrated ever since due to the club's failure to win major trophies. There have been speculations that the Chilean is keen on a reunion with former boss Guardiola at Manchester City and is yet to sign a contract extension with the Gunners. This also made signing Sanchez an economically profitable prospect as he would have come at €40 million or so.
Statistically, Alexis is one of the best players of the Premier League having scored 24 goals and 10 assists for Arsenal in the 2016-17 season.
With Alexis's contract at the Emirates expiring in 2018, Barcelona could have struck a deal which would have been economically viable for them. Who knows, it may well have turned out to be the bargain of the summer!